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The chem book I promised
    #1969413 - 10/01/03 02:35 PM (18 years, 26 days ago)

Assignment one:
Read pages 2-26 (below)
What will I learn in chemistry?

--Chemistry deals with the properties of chemicals--

Skipped, nothing worth typing is told in this part

--You use chemicals everyday--
All this part says is everything is made up of chemicals, skipped

--Aspirin is classified by it's properties--

Chemistry focuses on properties and reactions of matter like aspirin. Aspirin is a white crystaline compund with no odour and a
slightly bitter taste. The chemical name for aspirin is Acetylsalicylic acid. The term ACID signifies that it belongas to a
group of compounds with certain chemical properties (listed in tabel 1-1, below)
---TABLE 1-1---

-Water solutions of acids-
Taste sour, conduct electricity
turn blue litmus paper red
have pH values below 7
reAct with bases and certain metals to form salts

-Water solutions of bases-
taste bitter and feel slippery
turn red litmus paper blue
have pH values greater than 7
react with acids to form salts

The degree to which a compound exibits these properties is it's acidity. Acidity can be expressed numerically as pH. Acids have
a pH below 7 in water. Bases have properties that are somewhat opposite of acids, shown also in table 1-1(above).

The pH of aspirin in water is 2.7. Compare the acidity of aspirin to other familliar substances in tabel 1-2(below)

---TABLE 1-2---

Battery acid-0
Stomache acid, lemons-2
Tomatoes, bananas-4
pure water-7
Baking soda-9
Hand soap-10
Household ammonia-11

Your stomache is an acidic enviroment because certain cells in your stomache lining secrete hydrochloric acid, HCl.
Hydrochloric acid solutions are more acidic than aspirin. Aspirin irritates the lining of the stomache. People with ulcers
or other stomache problems cannot use aspirin.

Bufferin is the trade name for buffered aspirin. Buffering keeps the pH at a somewhat constant value even when an acid or
base is added. So using buffered aspirin could reduce stomache irritation, but does not remove the problem.
Aspirin could also be catagorized as an organic compound because it contains carbon. Hydrochloric acid is an example of an
inorganic compound since it contains no carbon.

--Chemical Reactions--

Felix Hoffmann began working on an alternate salicylic acid compound to relieve his fathers arthritic pain. At the time,
sodium salicyliate was being used and the standard dose was 6-8 grams daily. The effects of this dose were causing so much
discomfort to Hoffmann's father that he could no longer take it. Hoffmann searched for other compounds related to sodium
salicylate but that were less irratating. After testing the product on his father, Hoffmann found that acetylsalicylic acid
worked best. Hoffmann took his results to the president of the company where he worked, the Bayer company. As a result, the first
commercial aspirin was marketed in 1899. The name aspirin was selected by taking the A from acetyl and SPIRIN from spiracea,
a plant naturally containing salicylic acid.
Hoffmann's search on the literature available for salicylic compounds was an important part of his work. A literature se
arch is often the first step for a chemist trying to develope a new chemical or solve a problem. They often use Chemical
Abstracts (CA), the most comprehensive online source of chemical information in the world. CA contains abstracted versions of
over 18,000 scientific journals throughout the world.

--Aspirin is the product of chemical reactions--

You know from previous science courses that water, H2O, and sugar, C6H12O6, are made from chemical reactions. Figure 1-4 show
one synthesis used to make aspirin (below)

---Figure 1-4---
Benzene>Chlorobenzene>Phenol>Sodium phenoxide>sodium salicylate>Salicylic acid>acetylsalisylic acid(I simplified it)

Synthesizing aspirin involves a number of reactions in which the product of one step is the reactant in the next. Products
of a reaction are always shown to the right of an arrow. Reactants are always shown to the left. The information you see
printed over each reaction arrow indicate the conditions or reagents required for that reaction to occur. The process starts
with benzene, which comes from coal tar and oil. It is a raw material for many products like polyesterine and rubber. Chemists
have found many ways to represent benzene and compounds like it shown in figure 1-5(below)

--figure 1-5A--
shows the lines format of representing it

Figure 1-5B

Shows the abbreviated form of it (pentagon with lines where bonds are)

figure 1-5C

Shows the familiar representation, pentagon with a circle in the center.

Before a product is made available to the public, the synthesis is anylized to determine the difficulties and costs of a
large scale production. Because there is more than one way to synthesize acetylsalicylic acid, other methods must be anylized
as well.
Most production processes begin with a piloting stage before production begins. There are dramatic differences between
making a product like nylon in a lab and in a large scale production. Nylon production in the united states is about 2.6 billion
pounds per year.
Chemists and chemical engineers working on the large scale production want to make as much of it as possible for as cheaply as
possible. Pilot programs for any new production process allow chemists to monitor all aspects of the process to ensure that
standards for the product can safely and economically be met.
When the product is a drug, the manufacturing process must adhere to the strict saftey rules set by the US FDA. Less than
1 in 10,000 compounds synthesized by drug companies will ever make it to the consumer. Bringing a new drug to the market
generally takes about 10 years of research amd testing before production can begin.

---Working in the field of chemistry involves the Research, Development, and production of new materials---

Skipped, it details the areas of proffesional chemistry.

---Chemical production is a major industry---

The chemical industrial consists of those firms that supply the chemical compounds that are raw materials for other materials.
Sulfuric acid, ranked first, is also the top inorganic compound. It is the least expensive acid to produce and therefore a
desirable starting material for other compounds. Sulfuric acid is produced by burning sulfur and sulfur ores to creat sulfure trioxide.
Sulfur trioxide is then converted to sulfuric acid by adding water.
Nitrogen and oxygen, ranked second and third, are the two gasses most prevelant in the air. Both are obtained by liquifying
air. Nitrogen and oxygen have different boiling temperatures, so as the liquid air is warmed, the nitrogen boils off first.
Ethyline, ranked fourth, is the top organic compound on the list. Most ethyline is used in creating plastics. Ethyline is also a
starting material for ethyline dichloride, ranked thirteenth, vinyl chloride, ranked seventeenth, ethylbenzene, ranked nineteenth,
and styrene, ranked twenty-second.

--The chemical industry produces chemicals--

Skipped, just gives sales statistics on the top 25 chemical firms.

---The government regulates chemicals to reduce risk---
skipped, just gives lab safety tips and info on labels and the MSDS.

--Working with chemicals--
skipped, more safety tips

---Technology is using science to solve problems---
Chemistry differs from technology, which is the use of scientific principals to solve a problem. Determining the structure of
aspirin, an anylitical process, is chemistry. Using aspirin to relieve pain and reduce fever is technology. Using the
the structure of aspirin to produce other pain killers is technology.
Aspirin has a number of technological applications and has become a model for other pain relievers. This is an example of
how chemists can take a product, modify it slightly, and come up with a new product with more usefull properties and applications.
Because aspirin is a pure compound, there is no difference between the chemical action of name brands and generic brands.
However, aspirin can vary from brand to brand in terms of dosage, buffering systems, and the time it takes to act. Some
brands have a special coating that does not dissolve in the acidic atmosphere of the stomache, and therefore does not
iratate the lining of it.
You can now buy aspirin-free pain relievers like ibuprophen and acetiminophen. (skipped, basically it sounds like a sales

--------section review----------

1. Classify all the chemicals below as either organic or inorganic.

H2SO4 - sulfuric acid

N2 - Nitrogen

O2 - oxygen

C2H4 - ethyline

CaO - Calcium oxide

NH3 - ammonia

2.List four properties of H2SO4 (sulfuric acid).
3. How does technology differ from chemistry?
4. List three ways in which you can tell if an unknown chemical is an acid or a base.



---Scientific knowledge is gained from experiments---

When the early Romans and Greeks discovered how an extract could be prepared from willow bark to relieve a variety of ailments,
they undoubedly came upon this finding by trial and error. In their search, they must have tried a many extracts from a
variety of plants. Most of the extracts were probably useless, and some maybe even fatal. In the end, their discovery was
more one of chance than that of a well-designed plan.
Although these Greeks and Romans placed great reliance on rational thought and logic, they rarely felt it necessary to test
their findings or conclusions and did not feel inclined to conduct experiments. Gradually, experiments became the crucial test
for the acceptance of findings. Today experiments are an integral part of research in all sciences, including chemistry.
Science is distinguished from other fields of study in that it provides guidlines for research.
The way scientists carry out investigations or experiments is referred to as the scientific method. The scientific method
is a logical approach to exploring a problem or question formed from observations. In addition, this approach is designed to
produce a solution that can be tested and re-tested, and supported by experimentation. Although different representations are
used to to describe the scientific method, it consists of the fundemental activities outlined below.

-scientific method-
Observe and collect data that leads to a question

Formulate and objectively test hypothoses by experimentation.

Interperate results and revise hypothosis if necessary.

State conclusion in a form that can be evaluated by others


One distinguishing feature of science that separates it from other studies is the last step. The research findings of any
study must be reproducable by other scientists to be valid.
The biggest difference in the way discoveries are really made is how the question or problem is recognized. Sometimes
questions arise from accidental discovery. In turn these questions may lead scientists to search for an answer in one of
several ways. As examples, let's look at how two important drugs were discovered.

--Scientific knowledge is sometimes gained by accident--
skipped, just details the discovery of penicillin and cisplatain.

--The scientific method involves making educated guesses--
Recognizing and defining a problem or question stems from observation. The developement of cisplatain and it's usefellness
in treating cancer arose from one observation-Bacteria did not reproduce near the platnium electrodes. That observation led
to further experiments and tests. Once observations have been made, they are analyzed. Scientists start by observing all the
relevant or related information they have gathered. They look for related data to establish some relationship or conclusion.
Scientists then try to come up with a reasonable explaination for what they have observed. Any explaination they propose must
be testable. A reasonable explaination that can be tested is known as a hypothesis. Hypothoses are usually written using the if-then format
showing a cause-effect relationship. A testable hypothesis for Dr, Rosenburg's work with cisplatin is as follows: if cisplatin
can slow or stop cell reproduction, then it would be usefull in treating cancer.

--The scientific method involves experiments--
An experiment is a process carried out under controlled conditions to test the validity of a hypothesis. Dr. Rosenburg's work
with cisplatin initially involved the question of what was inhibiting the growth of the cells. The most important part of his experiments were
the control of variables. Before he could come to the conclusion that cisplatin was repsonsable for the cell inhibition, he had to measure
the effects of other conditions. How could he know if the effect was not caused by a simple temperature fluctuation in the
growth medium? How did he know the culture had not been contaminated? How did he know there were not changes in the electric
current? Because platinum is a generally inert element and the concentration of platinum compounds in the culture medium were
very low, it initially seemed unlikely that platinum could be causing the cells to stop reproducing.
Rosenburg had to narrow the field of possible variables by keeping them constant. Tempurature, current, purity of the platinum,
and the contents of the culture medium are some of the many variables that could change from experiment to experiment. By
keeping the variables constant, researchers can isolate the key variable. It took many experiments over a two year period for
Rosenburg and his team to verify that cisplatin was the key variable to stop cell growth.
Rosenburg's initial work spawned further research into cispatin's anti-cancer properties. After years of testing by independant
sources to verify the effectivness of the drug, cisplatin was approved for use in cancer chemotherapy.

--Data from experiments can lead to a theory--
Any conclusion that scientists make msust come directly and soley from the data they obtain in their experiments. Many times,
scientists find that they are unable to arrive at a conclusion. In fact, they may find that the data fails to support their hypothesis.
In that case, they must reexamine the data and form a new hypotesis to be tested.
Any hypothesis that stands up to repeated testing may become part of a theory. A theory is a broad generallization that
is based on observation, experimentation, and reasoning. Because theories are not facts, but rather explainations, they can
never be proven. A theory is considered successful if it explains MOST of what is happening and is updated as new information is discovered.
For example, you will learn about atomic theory in chapter three. The idea that all matter is made of discrete particles
called atoms that cannot be further divided was first proposed by democritis in 400BC. Using experimentation in the early 1800's,
John Dalton provided the data to support that theory. This theory has been modified as scientists discover smaller particles
that make up atoms.

--ModelS are like theories--
Models play a major role in science. They can take many forms, from actual replicas to written descriptions. Models can be used
in several ways. The structure of acetylsalisylic acid serves as the model for the development of other chemical substances
that can also be used as painkillers. They wave-partical model describes the behavior of electrons as waves and particals.
It is important to remember that models are not always exact. The model you see in figure 1-18 (3-D Depiction of aspirin
molecule) represents a molecule. The atoms are not hard spheres, nor are they the sizes or colors shown. However, the model
does show the geometrical arrangement of the atoms and their reletive sizes. When a model is an explaination, it explains
most of the observations. Models, like theories, are refined as new information is discovered.

--Scientific laws are based on fact--
Certain facts in science always hold true. Such facts are labeled as scientific laws. A scientific law is a statement or
mathematical expression of some consistancy about the behavior of the natural world. For example, motion is described by
newton's laws. Newton's first law is that if there is no net force acting on an object, and the object is at rest, it will stay
at rest.(or if in motion, continue in the same direction at the same speed). This law explains the movement or lack of movement
in all matter.
There are a limited number of laws in science compared to the number of theories and hypotheses. Do not confuse a scientific law
with either a hypothesis or a theory. A hypothesis predicts an event, a theory explains it, s law describes it.

-------------------section review----------------
1. What activities are part of the scientific method?
2. How do models help scientists acquire knowledge about the natural world?

---How do I learn chemistry?------
skipped, just says that scientists communicate through the internet.

--Themes help unify your study--
just explains the layout of the book in themes.skipped

----Macroscopic observations and micromodels----
Chemistry focuses on the observable effects pf the behavior of particles like atoms, molecules and ions. The observable effects
in the macroscopic world are acquired using the senses. Explaining these observations requires a model of what we believe
to be happening at the particle level. YOu will see numerous examples of this theme in the text illustrations. When you observe
a substance, you'll see a model of it's atoms, molecules or ions. When looking at a solid dissolving in water you'll look at a
breakdown of the solid's ordered structure. Understanding events at the particle level enhances your ability to explain what you observe
and make predictions.

----Systems and interactions----
A system is a collection of components that define something we choose to study. A system may be as large as the universe or as small
as the contents of a test tube. One goal of chemistry is to understand the interactions within a system.

----Equalibrium and change---
Equallibrium describes a state or condition of balance. In chemistry, equallibrium describes a reversable process occuring at the same rate.
One example of an equallibrium is a glass of salt water. When you add salt till no more salt dissolves, you have what is known
as a soluability equallibrium system. Dissolved salt is at equallibrium with the solid salt at the bottom of the glass. At the
macroscopic level it appears to be in balance. However, the equallibrium model explains that the solid salt is constantly
dissolving and the dissolved salt is constantly re-crystalizing. Because both processes occur at the same rate, the system
is in equallibrium. Disrupting an equallibrium system usually produces a noticable change.

Although you will study numerous examples of change throughout this course, there are some fundemental properties that are
conserved, such as mass, energy, and charge. Chemistry is more readily understandable and predictable because we know certain
things cannot appear and dissapear. For example, although mass is rearranged during a chemical reaction, it is conserved,
2H2 + O2 > 2H2O

----Classification and trends----
From your very first science course, you are taught to classify. Developing categories based on similar charectoristics or patterns of behavior
will simplify your study and reduce the need to memorize. In this chapter, you learned that there are two large classes of
compounds based on composition, organic and inorganic. You learned about two subclasses of compounds, acids and bases, which are categorized
by a certain set of properties. You will get a lot of proctice classifying and your understanding of classification will be
measured by your ability to make predictions.

---Theme's overlap----
Just says that all the themes are related and each chapter connects with the last.

---Study tips----
Give's study tips

--------------section review-----------------
What is a system? What is the system for the equallibrium example previously noted?

What fundemental properties are conserved during chemical change?

-Lesson one supplement-

--Structural representation--
Chemistry uses a language of symbols, formulas, and structural models to represent matter. For example, the illustration on
page two shows a connection between the macroscopic (an aspirin tablet) and the microscopic, (a 3-D model of an aspirin molecule).
Throughout the text, you'll see 3-D molecular models, which are drawn using computers to provide accurate depictions of reletive
size and geometrical shape. Careful observation of each will help you visualize the actual particals.
In everyday life, you deal with many compounds that chemists classify as acids. This class of substances includes many
powerful chemicals such as nitric acid and sulfuric acid. A simple numeric scale, called the pH scale, expresses the acidity of
a solution. The scale begins at 0 and ends at 14.

--Organic and inorganic Classifications--
Matter can also be classified as organic or inorganic. Organic chemistry is unique in that all compounds classified as organic
contain carbon, while inorganic chemistry deals with the other elements. Exceptions to this rule are carbonates, molecules who's
formula's contain CO3, and oxides, molecules who's chemical formula's contain CO and CO2, which contain carbon but are generally
reguarded as inorganic.

---Scientific method---
A great scientific discovery is occasionally made by accident, but most advances in science are made by applying the scienctific method.
The scientific method is a logical, organized way of answering questions by using experimental investigations. It consists of four broad
activities shown on page 16 of your workbook. These activities are repeated untill all hypotheses have been exhausted and all
observations have been explained. Experimental results are subject to scrutiny till verified by other scientists.



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Registered: 05/10/01
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Re: The chem book I promised [Re: rommstein2001]
    #1969424 - 10/01/03 02:38 PM (18 years, 26 days ago)

Assignment Two - read pages 32 through 64 now.

Chapter Two - Matter and energy

--What is matter?--
What do air, your brain, a star, and a peanutbutter sandwich all have in common? All these things are examples of matter.
Matter, the "stuff" of which all things in the universe are composed, comes in a fantastic variety of forms.

--Matter has mass and volume--

Matter is defined as anything that as mass and volume. What do we mean by mass and volume? Volume is simply the amount of
space an object occupies. A grapefruit has more volume than a lemon, for example.
The mass of an object is a measure of how hard it is to change the objects state of motion. You can compare masses of different
objects by pushing or pulling them. Very massive objects are reletively hard to start or stop moving. Common units of mass are
the gram(g), kilogram(kg), and milligram(mg). Mass also indicates the amount of matter within an object; the more massive an
object is, the more matter it contains.
Note that mass is similar to weight, though strictly speaking they are not the same thing. The difference is that weight depends
on gravity, while mass does not. Since gravity varies from place to place, weight also varies, but mass is constant because
it does not rely on gravity.

--A balance measures mass--
Weight can be measured using a scale. To determine mass you need to use a balance. In chemistry, you will generally be interested
in mass rather than weight, so the balance is standard lab equipment. Two types of balances that you may use are analytical balances
and triple beam balances.
Although the term "weigh" is not literally equivilant to "determine the mass of", these expressions are often interchanged.
In chemistry, when you hear the term "weigh", you may actually need to determine the mass. Check to be sure.

--Atoms are basic units of matter--
Imagine crushing some coffee beans in a grinder. Imagine crushing them into a fine powder. Each of these fine grains contains
billions and billions of sub-microscopic atoms.
Matter in and around you is made of atoms. There are over 110 different atoms in the known universe, but together they make
up everything around you.
Atoms do not usually exist by themselves, but combine to create compounds. Some of these clusters are called molecules. A
molecule may contain two atoms or a thousand, but in any case a molecule bahaves as a unit. Most materials in your enviroment
are made of many different kinds of molecules which are mixed together. An orange peel, for example, contains more than 100 kinds
of molecules.

---Properties of matter---

-Matter can be described by it's properties-

Chemists describe different types of matter by listing their charectoristics, or properties. Color, mass, volume, texture,
transparency, flamability, and taste are a few of the many properties that are usefull in describing matter.
Ever since the earliest humans sought flamable material for making fire, people have been collecting information about the
properties of matter. Collected data from the history of chemical investigation is compiled in reference books that are easily available to you.

--Physical properties are usefull for identifying things--

Color, texture, shape, and mass can all be observed or measured without changing the composition of matter. Properties such as
these are called physical properties.
You rely on physical properties to identify things all the time. Using color, texture, and mass, it's easy to determine which recycling bin a piece
of white paper or a brown glass bottle belong in, for example. Even in a photograph, you can probably identify matter by
observing the physical properties.

--State of matter is a physical property--
An easily observed property is state of matter. Solids, liquids, and gasses are the common states of matter.
Solids have a fixed volume and shape. These features result from the way solids are structured on a microscopic
level. In the solid state, atoms and molecules are held tightly in rigid structures but vibrate slightly about fixes positions.
Liquids have a fixed volume but a variable shape. The particles in liquids are not held together in the rigid manner
charectoristic of solids. Like ball-bearings in oil, the particles in liquid can slip and slide past one another. As a
result, liquid as a whole is able to flow. The distance between adjacent particles are constant on average, so the overall
volume is fixed.
Gasses have no fixed shape or volume therefore they expand to fill any container they occupy. In a gaseous state, a few grams
of helium would become evenly distributed in a glass jar or throughout a large room. This behavior is due to the fact that
their particles are not held to one another. Instead, they are free to move about.

At very high temperatures, matter can exist as plasma, a fourth state of matter. In this high energy state, atoms are torn
apart into smaller pieces. The sun, stars, and much intergalactic matter, and the glowing inside of a flourescent lamp are all
examples of plasma. A fifth state of matter, that of the neuron star, has recently been discovered. Little is known about this state.

--Chemical properties tell how substances interact--

A material is not fully described by physical charectoristics alone. Left out of the description is how it will react when in
contact with other materials. To describe this type of behavior, we refer to chemical properties, properties which are observable
only when a substance reacts with another.
Reactivity with acids, for example, is a chemical property. Calcium hydroxide, an ingredient in some antacids, is very reactive with acids.
It is used to neutralize excessive amounts of Hydrochloric acid that form in the stomache. Reactivity with acid can sometimes
have destructive effects, such as buildings/statues deterioration.
Reactivity with oxygen is another chemical property, such as the browning of some fruits when exposed to air.

--Intensive properties result from the way matter is structured--
Some properties of matter, such as mass, volume, and leangth, depend on the quanity of the matter present. These are called extensive properties,
But all chemicasl and many physical properties do not depend on the amount present. These are called intensive properties.
For example, consider graphite, the material that makes up your pencil "lead". Graphite is a gray solid at room temperature
and has a slippery texture no matter if it's in the tip of your pencil or in a laboratory reagent flask. Graphite has these intensive properties because
of the way the atoms are arranged.

----------Section Review--------
Tell whether this is a chemical or physical property: Iron is transformed into rust in the presence of air.

---How do matter and energy interact?---

Much of chemistry is about creating new substances to improve food, fuel, health, and fashion. Chemists can put molecules
and atoms together indifferent ways or take them apart. When atoms form molecules, or when molecules break down into atoms,
energy is involved. Energy plays an essential role in chemistry. Energy is a broad subject, but a good basic description is
energy is the capacity to move or change matter.

--Forms of energy--

Kinetic energy is a type of energy that only moving objects have. A truck roling down an alley sets objects in motion or changes them as he runs into them. The roling truck has energy; it can move or change matter. Because the truck's energy rises from motion we call it kinetic energy. The amount of Kenetic energy, KE, in an object depends on it's mass, m, and velocity, V. Kinetic energy is easy to calculate from the following equation:

Kinetic energy= 1/2 (mass)(velocity)^2 (when I type ^2 I mean squared) KE=1/2mv^2

Energy is measured in units of kg*m^2/s^2, or joules, J. One joule is about equal to the energy you expend bringing a hanburger to your mouth. It is easy to bring the expression for kinetic energy to other situations as well. For example, the typical cheetah has a mass of 60kg. It's peak speed is about 28m/s. Putting these into the eqation below:

KE=1/2mv^2 = 1/2(60kg)(28m/s)^2 = 2.4*10^4J.

The kinetic energy of a typical oxygen molecule is also easily calculated. At room temperature and average pressure, an average oxygen molecule moves at a speed of about 400m/s. It's mass is 5.3*10^-26. Puttin these into the equation:

KE = 1/2mv^2 = 1/2(5.3*10^-26)(400m/s)^2 = 4.2*10^-21 J

--Potential energy is stored energy--

Potential energy is energy an object posesses because of it's position. It is called potential energy because it has the potential to move or change an object once the energy is released.
An objects potential energy is related to the amount of force required to keep it in that position. For example, there is potential energy in a compressed spring. Force must be applied to keep it in place.
Matter held in an elevated position is subject to the downward force of gravity, so forces are required to keep it in place. Therefore an elevated object has more Potential energy. Which has more potential energy, a car parked on a small hill or the same car parked on a mountain?
Potential energy also influences the behavior of atoms and molecules. Strong forces hold these small particals together, as a result, clusters of these particles contain potential energy.

--Kinetic and potential energy underlie other energy forms--

There are many kinds of energy, from wind to solar to nuclear to electric to sound energy. In the macroscopic world, it makes sense to talk about these diverse forms of energy. But when you consider these forms of energy on an atomic level, they are not truly unique. They are just Kinetic energy, potential energy, or combination of both acting on small mass particles. KE and PE underlie electric, solar, and other forms of energy we encounter and see as distinct.
One of the important forms of energy to consider when studying matter is internal energy. Internal energy is the sum of all the kinds of energy within a substance. This includes potential energy between atoms and molecules and kinetic energy due to the movment of atoms and molecules. As the temperature of a substance increases, the motion of it's atoms increases, as does it's internal energy.

--Energy can be transformed--

The hydroelectric plant is an example of how energy can be transformed. Hydroelectric plants transform the potential energy of elevated bodies of water into Kinetic energy of rushing water, and finally to electric energy.
Energy is transformed continually around you. The internal energy of a flashlights battery is transformed to electric energy, then to light energy when the switch is flipped on.

--Relating mass and energy--
-mass is a form of energy-

In 1905, Albert Einstein shook the world with his discovery of a third fundemental type of energy. This third type of energy is a familliar quantity, mass! This idea is described in einstein's famous equation:

E represents the energy of an object, m it's mass, and c the speed of light. Light travels at a constant speed of 3*10^8 m/s.

Besides being the amount of material in an object or measure of the difficulty of changing the motion of an object, mass is also a form of energy. One way to look at it is mass is the energy of being. Consider a basketball, if it is moving it has kinetic energy. If it is elevated it has potential energy. Even resting on the ground it has energy. as gravity is acting on it and it has internal energy. But beyond this it has another type of energy - it's mass energy. It's masss energy is not due to it's motion, position, or internal forces, but the very fact of it's mass.
Mass, like all other forms of energy can be transformed. In transformations, a small amount of mass corresponds to a huge amount of other types of energy. In nuclear reactors, the masses of particles are converted to kinetic energy, which is transformed to electric energy.

--Energy cannot be created nor destroyed--

In previous examples, you found that energy can be converted to other types of energy. Energy is also often transfered betewen objects. Energy transfer in the form of heat occurs when two objects of different temperature are put into contact with one another. When energy is transferred or changes form, no energy can be created or destroyed. The law of conservation of energy is the formal statement of this principal. The law of conservation of energy states that enrgy cannot being created or destroyed; it may be tranformed or transferred, but the total amount of energy in the universe never changes.
The law of conservation of energy can be applied to closed systems smaller than the universe as well. Closed systems, or well defined groups that are free to transfer energy only to one another, demonstrate energy conservation. Chemicals in a stoppered, insulated reaction flask approxminate such conditions. The total energy of the flask does not change, although the molecules and atoms are free to transfer energy to one another.

----Matter Changes----

--Physical changes do not affect chemical composition--

Before glass is recycled, it is crushed so that it will take up less space. This crushed glass is known as cullet. When this cullet arrives at the factory, it is melted and poured into moulds in the shape of new bottles and jars. In the recycling process, glass goes through several physical changes such as crushing and melting. A physical change is a change that affects physical properties only. Chemical properties are unaffected.

--Change of state is a physicAL change--

For a gram of ice to turn from the solid state to the liquid state, 333J of energy are required. Why is this energy needed? To see why, picture what is happening on the molecular level. For a solid to melt, it's atom's or molecule's must begin to move vigourosly enough to partially breaK free of it's neighbors and break down the solid crystal structure. The atoms and molecules require energy input to increase their own kinetic energy. This energy is most often supplied as heat.
Boiling, the rapid change from liquid to gas, requires even more energy- 2260J per gram. In boiling, atoms or molecules need enough energy to break totally free of their neighbors. Melting and boiling are called endothermic changes because they take in energy in the process. When a gas cools to a liquid or a liquid to a solid, it goes from a higher to a lower energy state. The energy given off by the atoms is transferred to it's surroundings as heat. Such changes, in which energy is given off as opposed to taken in, are called exothermic changes.

--Chemical changes alter chemical composition--

In a chemical change, one or more substances are changed into new ones. This change occurs at the atomic level, where atoms are changed or rearranged without change in the total number of atoms.
You learned in chapter one that those substances undergoing chemical change are the reactants and those created in the change are known as products.
All chemical changes are accompanied by transfers of energy. Like changes of state, Chemical changes are either exothermic or endothermic, depending on whether they accept or release energy. In an endothermic reaction, the product has more energy than the reactant does.

----How is matter classified?----

---Mixtures and pure substances---
--Matter can be classified as either a pure substance or as a mixture--

A pure substance is matter made of only one type of atom or molecule. A mixture, on the other hand, is a collection of two or more pure substances physically mixed together and cannot be represented by a chemical formula.
The proportions in a physical mixture can vary. For example, chicken soup is a mixture which can contain different proportions of chicken, salt, celery, carrots, onions, or pepper, depending on the recipe.
A pure chemical has specific chemical and physical properties. Any sample of pure water is odorless, clear, and will produce bubbles of hydrogen gas if introduced to calcium. As you can expect, one rarely finds pure substances in nature or in the laboratory. Therefore, "pure" is really a reletive term. If given a substance with such a small amount of impurities that the impurities can be ignored, the sample is considered pure.

--Mixtures can be further classified--

Mixtures can further be classified as either homogeneous or heterogeneous. A homogeneous mixture is one in which the ingredients are uniformly distributed. Gasoline, saltwater, and syrup or homogeneus mixtures. All regions of a homogeneous mixture are uniform in their properties and composition.
A heterogeneous mixture is one in which the substances are not evenly distributed. Some regions of a heterogeneous mixture may have different properties from others. Some examples are oil and vinegar salad dressing, skin, apple, juice, and salads.

--elements are the simplest pure substances--

Aluminum, copper, oxygen, and silicon are some elements that may be familliar to you. Elements are the simplest of pure substances, because they contain only one type of atom. For example, a piece of elemental silicon contains many billions of atoms, all of which are silicon atoms.
Every element has it's own unique set of physical and chemical properties. Once purified, gold mined in africa today is the same as gold mined in california gold rush or by the aztecs centuries ago. Pure gold, from any source, is the same substance. It is an unreactive, soft metal that melts at 1064 C.

--A small number of the elements make up most common substances--

Although there are 109 different elements, only about a dozen make up what you notice every day. By far, the most common element is hydrogen. More than 90% of the atoms in the known universe are hydrogen. The elements oxygen and silicon make up 70% of the earths crust. Living things are comprised mostly of four elements, carbon, hydrogen, oxygen, and nitrogen. These four molecules combine to create the thousands of molecules necessary for life.

--Elements may consist of atoms or molecules--

An element may be made of individual atoms, or molecuals. For example, the helium gas in balloons consists of individual helium atoms. If an element is comprised of molecules, those molecules are made of just one type of atom. For example, nitrogen, found in the air, is found in the molecular state. Each nitrogen molecule consists of two nitrogen atoms joined together. For this reason, nitrogen is called a diatomic gas. Oxygen, another gas found in large amounts in the air, is also a diatomic gas.

--Some elements have allotropic forms--

A few elements, notably oxygen, phosphorus, sulfur, and carbon, are unusual because they exist as allotropes. Allotropes are a different molecular form of an element in the same physical state. One allotrope of oxygen is the diatomic air you breath. Another allotrope of oxygen is ozone, ozone molecules contain three oxygen atoms.
The properties of allotropes can vary widely. Diatomic oxygen is a colorless, odorless gas essential to life. Ozone on the other hand is a blue, toxic gas that can sometimes be smelt after an intense thunderstorm. Lightning provides the energy needed to convert the diatomic oxygen in the atmosphere to ozone. Carbon has several interesting allotropes in the solid form. One allotrope is graphite, the slippery gray solid that you read about earlier. Diamond is another carbon allotrope.
In the 1980's, a carbon allotrope consisting of molecules with 60 carbon atoms was discovered. This allotrope was shaped like the geodesic dome designed by the innovative american philosopher and engineer Buckminster Fuller. For this reason, The 60 carbon atom molrecules are called "bucky-balls". More recently, another carbon allotrope has been discovered, the "bucky-tube". Both Bucky-balls and Bucky-tubes exhibit super-conductivity, that is, to conduct electricity with no wasted energy.

--Compounds can be seperated into elements--

Pure substances that are composed of two or more different elements and are chemically combined are called compounds. Compounds are created when atoms of different elements are joined together in a chemical reaction.
Carbon monoxide is an example of a molecular compound. Molecular compounds are made of molecules. Some compouds, such as table salt, are not made of seperate molecules. Table salt, or sodium chloride, is an ionic compound. Ionic compounds, like molecular compounds, are made of at least two different elements that are chemically joined. However, an ionic compound is not made from discreet molecules. Instead, atoms are distributed in a continuous network. You will learn more about molecular and ionic compounds in chapters 5 and six.

--Every compound has a unique set of properties--
Because a compound is a pure substance, you know that it has a unique set of physical and chemical properties. You may be surprised to find out, however, that the properties of the compound may be very different from the elements that compose them.
A set of elements can often create more than one compound. Carbon monoxide and carbon dioxide are examples of two very different chemicals made from carbon and oxygen. Carbon dioxide is used in some fire extinguishers to put out fires, while carbon monoxcide burns when ignited. Carbon monoxide is toxic, while carbon dioxide is the gas you exhale as you breath.

--Compounds can be distinguished from mixtures--

You guys know the difference, right? No need to repeat...

----How are substances identified?----

---Methods for seperating mixtures---

--Mixtures can be seperated by physical means--

The photographs in figures 2-24 and 2-25 (picture showing a magnet crane in a scrapyard sortingn steel etc from non-magnetic substances, a salt pond evaporating,a centrifuge, and a man decanting something) show some of the many ways to seperate a mixture using only physical means. When you filter, evaporate, centrifuge, or decant a mixture you bring about only physical changes. The substances obtained afterwards are no altered chemically.

--Chromatography is widely used in industry--

Chromatography may be used to seperate components of a solution so they may be identified. Chromatography works because different substances have different attractions to solvents and other media.
Paper chromatography is used to seperate black ink into the colored dyes it contains. How does this work? Water dissolves the ink, the ink travels up the paper with the water, Substances travel at different rates according to their attraction to the paper. Those most attracted to the paper travel the slowest. They appear on a reletively low point on the paper.
Research labs make great use of chromatography. The food industry uses gas chromatography to isolate and identify the gasses that give food it's aroma. Some of these pleasant smelling compounds can be used in artificial flavoring or in fragrances.

--Distillation can be used to purify salt water--
Distillation is a method of seperating substances that have different boiling points. Figure 2-27 shows a setup that can be used to seperate salt from saltwater solution (shows a distillation setup, distillation flask, cold water condenser, and collection flask.) Salt water is placed in the distillation flask, where it is heated till it evaporates. As the steam travels down the condenser it condenses back into water, which drips into the collection flask, leaving the salt behind.

>>>I'll post a couple interesting articles about both chromatography and distillation later.<<<

--Density is a constant ratio of mass to volume--

Table 2-2 \/ \/ \/

sample number mass volume(mL)

1 5.00 .443
2 15.0 1.33
3 24.0 2.12
4 52.0 4.6
5 64.0 5.66
6 81.0 7.17
7 95.0 8.41
8 101 8.94
9 142 12.6
10 153 13.5


A relationship between two quantities, such as mass and volume, can be represented on a graph. (OK, for the next two paragraphs it explains that mass is directly proportional to volume in lead. It then says that the slope (slope=y-axis/x-axis on a graph, on this mass is represented on the Y axis and volume on the X axis) has a value of 11.3.
The equation for density is D=m/v and is expressed in grams per mL, so the density of lead is 11.3g/mL.)

--Density can be used to identify substances--

This simply says that if you have an unknown pure substance, such as a bracelet you believe is silver, You determine the density of the substance, than look up the suspercted materials density, and there ya have it.

----Section Review----
Can iron oxide (rust) be seperated into oxygen and iron by chromatography? Why or why not?

---How should data be represented?---

--Standard Units--

-SI units are used in science-

Here is a list of the seven SI (systeme internationale) units.

Quantity unit symbol

Leangth | Meter | m

Mass | Kilogram | kg

Time | second | s

Electric | ampere | A

Thermodynamic| Kelvin | K

Amount of | mole | mol

Luminous | candela | cd

Some of the prefixes used

prefix symbol meaning

giga | G | billion

mega | M | million

kilo | k | thousand

deci | d | thousandth

centi | c | hundreth

milli | m | thousandth

micro | u like thing| millionth

nano | n | billionth

pico | p | trillionth

--Kelvins are used to measure temperature--

Kelvin/Celcius/Fahrenheit comparison

Freezing point of water

F: 32
C: 0
K: 273

Celcius and kelvin are easily converted between one another. To convert from celcius to kelvin, simply add 273.16 to the measure, or do the opposite for converting K to C.

The next part is skipped, just be sure to make accurate measurements.


Chapter two supplement

Atoms: units of matter

Matter is composed of seperate, tiny particles called atoms. If we took a piece of matter and divided it and subdivided it we'd eventually come to a piece that could no longer be divided and still have copper. This particle is an atom. When several atoms are joined together so tightly that they act as a single unit, this is known as a molecule. A substance containing the unified atoms of more than one element is known as a compound. A molecule is the smallest unit of a compound.

Physical states of matter

Ordinary matter can exist in three states: Solid, liquid, and gas. The differences among these results from differing molecule arrangement. Solids are tightly arranged and have fixed volume and positions, liquid has fixed volume but since the molecules are loose enough to move about freely has no fixed shape, and gas has neither fixed shape nor fixed volume, the molecules are entirely free of one another.

Exothermic and endothermic changes

In some reactions, heat is needed to make them go. These are known as endothermic. In others, heat is given off, this is an exothermic reaction.

Compounds and mixtures

A mixture is two or more substances physically mixed, but they keep their individual properties. A compound is A new chemical formed by two or more reactants that has an entirely new set of properties. For example, if we mix sulfur and iron together, do we have a compound? No, it can still be seperated with a magnet. If the mixture is heated, however, the two combine to form iron sulfide, a non-magnetic substance.



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Re: The chem book I promised [Re: rommstein2001]
    #1969460 - 10/01/03 02:49 PM (18 years, 26 days ago)

Assignment 3

read pages 72 through 100


This part is skipped, I?ll post some info about how the periodic table of elements is organized later, I wanna hurry and get to some more complex (but still easy) stuff.

---What is the structure of an atom?---

--Building the atomic model--

Figure 3-2b shows an atom bomb exploding. Because the atom bomb and atomic energy have had such an impact on modern life, the current age has been dubbed the atomic age. In such an age, people take the existance of atoms for granted. But no one has ever directly seen an atom. Scientists rely on the massive amount of evidence to infer their existance.

--evidence supporting the atomic theory--

Recall that the idea that matter is made up of atoms can be traced back to 400 BC. But ancient greeks were better theorists than experimentors, they rarely felt compelled to test their findings. Experimental results didn?t appear for about 2000 years, in 18th century europe. There, the early "chemistry investigators" noticed that there are certain charectoristics shared by all chemical compounds. The observations made by them lead to three laws that describe how compounds are formed.
1: Law of definite composition
A compound contains an exact proportion of elements reguardless of the size of the sample.

2:Law of conservation of mass
When two or more elements react to form a compound, the total mass is the same in the end as in the beginning.

3:The law of multiple proportions
The law of multiple proportions applies to different compounds made of the same elements, such as water and h2o2. It states that mass ratio for one element can be combined with fixed ratio of another element to form small whole numbers.

As usefull as these law?s were, no one realized the true potential untill John Dalton demonstrated that taken together, these laws prove the existance of atoms.
Dalton argued that these laws could not be explained without acknoledging that all matter is made of atoms. This reasoning led to the modern theory of the atom. Dalton?s early theory contained 5 basic principals:

1. All matter is made of indivisable and indestructable atoms.
2. Atoms of a given element are identical in their physical and chemical properties
3. Atoms of different elements have different chemical and physical properties.
4. Atoms of different elements combine in simple, whole number ratio?s to form compounds.
5. Atoms cannot be subdivided, created, or destroyed when they are combined in chemical reactions

While exceptions have been found to these, the theory itself has never been scrapped, simply updated with the discoveries.

---Finding the structure of the atom---

--Electrons are negitively charged particles with small mass--

Experiments made in the mid 1800?s led to major alterations to Dalton?s theory. The atom was found to be not indivisable at all, in fact was made of smaller particles. The first evidence of this was discovered by scientists interested more in electricity than in atoms. These researchers studied the flow of electricity in glass tubes with metal disks, electrodes, postioned on either end. When the electrodes were connected to a source of voltage and most of the gas removed, current flowed through the tube and the remaining gas began to glow. The beam always originated at the negetive plate, or cathode, and traveled towards the positive one, the anode. For this reason the tubes were named cathode ray tubes and the rays cathode rays. They are still used today in TV?s and CRT computer screens.
The researchers observed that by places a small paddle wheel in the tube, the ray would push it towards the anode. This suggested that there were small, individual particles that composed the rays to push it down the tube.
In 1897, J.J. Thompson noticed that electrically charged plates or magnets disrupted the normally straight path of the cathode rays. The direction of the change indicated that the particles must be made of negetively charged particles. G. Johnstone stoney named these negetively charged particles electrons.
Experiments were later conducted to determine the size of the electrons. They were determined to be nearly 2000 times less massive than that of the smallest atom, hydrogen. The lightness of electrons implied that there must be other, heavier particles to account for the mass of atoms. There was other evidence that other particles existed as well. Atoms were known to electricly neutral. This meant that positively charged particles must be present to cancel out the electrons. Thompson created a model to express his findings. This model, dubbed the "plum-pudding" model, showed the atom as a positively charged ball with negetive electrons embedded within.

--Each atom has a positively charged inner core--

A student of Thomson, Ernest Rutherford, assembled a reasearch team to perform an experiment that ultimately disproved the plum-pudding model. This is the now famous "gold-foil experiment". Rutherford?s team direct small positively charged particles, "alpha particles" at a very thin sheet of gold foil. The team measured the angles of the beam as they were deflected off their straight path. This method was much like determining the shape of an object under a table by roling marbles at it.
The experiments revealed that most of the particles shot straight through it. Rutherford reasoned that this was die to the empty regoins on the foil, The team also observed that some of the particles came out at a slight angle. But what really surprised the team were the particles that were actually scattered back. Rutherford reasoned that that deflection was due to the positively charged alpha particles and the positively charged matter within the atoms. However, if the positive charge was spread out througout the atom as the plum pudding model depicted it, this would not have been possible. The positive charge must be concentrated within atoms to scatter the alpha particles backwards. Rutherford had discovered the positive core of the atom. The tiny central region of the atom was named the nucleus, from the latin word meaning little nut. Electrons, Rutherford supposed, traveled around the nucleus in much the same way the planets travel ?round the sun. The nucleus, then, is the dense central portion of the atom that contains all of the positive charge and most of the atom?s mass. By calculating the number of alpha particles deflected the average size of the nucleus was determined to be at least 10,000 times smaller than the radius of the whole atom. To put this reletively, if a marble was the nucleus, the whole football stadium would be the atom.

--electrons occupy energy levels within an atom--

Classic physics predicted that, since all accelerating charged particles radiate energy, the circulating electrons in Rutherford?s planetary model must also radiate energy. As the energy radiated, it would be lost and the electrons would fall out of orbit. The electrons would be destroyed in a billionth of a second. Yet most atom?s are known to stay stable for thousands of years. Clearly, something was wrong with Rutherford?s model.
In 1913, Niels Bohr, a young Danish scientist, came up with a model that addressed the deficiancies in Rutherford?s model. Bohr proposed that electrons could only reside within specific energy levels. This is similar to the rungs of a ladder. A person can move up and down the ladder only by standing on the rungs, it is impossible to stand between the rungs. Similarly, the Bohr model predicted that a molecule can only reside in the energy levels.
Energy levels close to the nucleus have lower energy levels than those further away. An electron must gain enough energy to move from a lower to a higher energy level. The amount of energy required for this jump is known as a quantum. Thus, the Bohr model shows that the energy of an atom is quantized, it cannot have an arbitrary value of energy, only specific values are possible.
The quantization of energy in an atom is unlike anything you can experience in the macroscopic world. If a child?s swing behave this way, you?d only see the child at certain angles, it?d jump from say 0deg to 3 to 9 to 15, the child would never been found between!

--Neutrons add mass to the nucleus--

The positively charged nuclear particles that repelled the alpha particles in Ruthford?s experiment were found to be quite heavy, the mass of one is nearly 2000 times that of an electron. These particles were named protons.
The mass of the proton posed a dillema because the mass of all the atoms besides hydrogen were known to be larger than the total mass of their protons and electrons. Clearly there must be another particle conttributing to the mass of an atom. The search for a third subatomic particle was soon underway. This particle proved harder to find, because unlike protons and electrons, this had no electric charge. Irlene Joliot-Curie discovered that when beryllium was bombarded with alpha particles, a high-penetrating beam was formed. James Chadwick discovered that this beam was composed of particles reletively the same mass of protons.
With the discovery of neutrons, the model of the atom was thought to be complete. The atom consists of protons and neutrons, which took up most of the mass of the atom, which was circled by negetive electrons, with neglegable masses. Is this model of the atom still accepted truly complete?

---The modern view of the atom---

--Electrons can be described as particles or waves--

Electrons were first recognized because they were seen to push a paddle wheel down a cathode ray tube. Other experiments on the light emitted by energized, gaseus atoms also indicate electrons as particles.
When all electrons are in the lowest possible energy level, the atom is said to be in a grounded state. When an atom absorbs energy so that the electrons are boosted to higher energy levels, the atoms is said to be in an excited state. Experiments on gaseus atoms indicate that they absorb energy from an electric discharge to reach an excited state. Later, the atoms return to their ground states by emitting the energy they have absorbed, as light.
The light emitted by an element when it?s electrons return to lower energy levels can be viewed as a bright-light emission sppectrum. The spectrum is obtained by passing the light an element emits though a prism to seperate it into the various colors it contains. Each colored band represents the light energy released by an electron when it returns from an excited state to a lower energy level. The energy of each band is equal to the difference between the original and final energy levels of the electron.
When sunlight is passed through a prism, the visable sprectrum, all colors visable to the naked eye, are displayed.
This visable spectrum is a small portion of the largr electromagnetic spectrum. The electromagnetic spectrum consists of the various classes of electromagnetic waves: microwaves, radio waves, X-Rays, gamma rays, infrared radiation, and ultraviolet radiation, in addition to visable light. All electromagnetic waves are essentially the same, they are electromagnetic vibrations travelling through space in the form of waves. However, the waveleangth and frequency of the waves differs. The waveleangth of a wave is the distance between two identicle points on a wave, such as two peaks. Frequency is the number of waveleangths that pass in a certain time, usually a second.
All electromagnetic waves are created by accelerating charged particles. The radio waves that transmit the signals are created by the motions of electrons moving up and down the antenna wire. The visable light is produced by the jumping and falling of electrons in atoms. In falling, the electrons move closer to the nucleus. Electrons, then, have properties of particles, as evidenced by their behavior in cathode ray tubes and their ability to jump and fall. Electrons also have properties of waves. However, electrons have tiny waveleangths, on the order of 10^-10m. Thus, electron waves are much smaller than visable light waves. Because of this, the wave behavior of electrons can only be viewed on a very small level, such as atoms. The electron microscope provides evidence of the wave behavior of electrons.
Because electrons have properties of both particles AND waves, a new model had to be developed. This new model was produced by quantum theory.

(ok, we?re almost to my favorite part!)

--Quantum theory provides a modern picture of the atom--

The description of the atom that is build on the wave properties of the electron is the quantum theory. The quantum theory uses the complex mathematical equations of quantum mechanics to describe waves. The quantum model is an essentially a mathematical one, and cannot be represented by anythign that exists in the macroscopic world.
Like the Bohr model, the quantum model predicts quantized energy levels for electrons. Unlike the Bohr model, the quantum model used today does not predict the exact location of the electrons. It is conserned with the probability of finding the electron in a certain position.
When all of the probable locations of the electron are plotted on a graph, they indicate the region where the electron can be found. These regions are known as orbitals. Each orbital can be occupied by up to two electrons. Note that the boundries of the orbital are fuzzy because the likelyhood od finding an electron changes gradually throughout the region. Regions with the densest concentration of points are areas where the electron is most likely to be found. Due to their fuzzy boundries, orbital are sometimes called electron clouds. Just as the blade of a fan could be anywhere within it?s blurred path, the electron could be anywhere in the electron cloud.
It is conventional to draw a surface around the orbital to signify where the electron can be found 90% of the time. With this technique, it is possible to simplify the model while keeping it basically accurate.
The position and velocity of an electron can be measured, but the presision of these measurements is limited. The quantum theory shows that reguardless of how advanced society becomes, it will never be able to measure both an electrons position and velocity simutaniously. This fact is known as the Heisenberg uncertainty principal. You can never know how fast an electron is moving if you know where it?s at, and you can never know where it?s at if you know how fast it?s moving.

--The atom is a scientific model--

If atoms all consist of electrons, protons, and neutrons, how then, is every element different? As you know, atoms differ not in the type of subatomic particles they contain, but in the number.

--Each element has an atomic number--

The number of protons in the nucleus of an atom is known as it?s atomic number. Hydrogen, with the atomic number of one, contains one proton in it?s nucleus. Oxygen has an atomic number of 8 and contains eight protons. If you an elements atomic number, then you also know how many electrons an electricly neutral atom of that element contains. Such an element must contain the same amount of protons as electrons to be neutral, thus, nitrogen, with an atomic number of 7, contains seven electrons, and seven protons.

--Isotopes of the same element have different mass numbers--

The number of protons in an atom is fixed, so all atom?s of the same element have the same atomic number. However, the number of neutrons can vary. Atoms of an element with the same number of protons but a different number of neutrons are known as isotopes.
Consider the simplest element, hydrogen. Three isotopes of hydrogen exist, protium, deutrium, and tritium. Each hydrogen isotope contains one proton in it?s neucleus. But protium contains no neutron, while deutrium has one and tritium two. Despite their differences, isotopes have very similar properties. Can you see why?
In addition to having an atomic number, each element also has a mass number. The mass number is the total number of protons and neutrons in the nucleus. An isotope is represented by it?s chemical symbol with two additional numbers to the left of it. The mass number is written as a superscript and the atomic number as a subscript.
A second way to represent isotopes is to write both the element?s name and mass number. For example, deutrium would be hydrogen-2 and tritium hydrogen-3. The two isotopes of oxygen are oxygen-16 and oxygen-18..

--The number of neutrons in an element is easy to find--

If you know the atomic number of an element, you know how many protons and neutrons it contains. If you know the mass number as well, it is easy to calculate the number of neutrons. Simply subtract the atomic number from the mass number.

--Labeling electrons in atoms--

--Quantum numbers are used to differenciate among electrons--

In quantum theory, each electron in an atom is assigned a set of four quantum numbers. Three of these numbers give the location of the electron, the fourth describes the orientation of an electron in an orbital. The first quAntum number, represented by the letter "n", is called the principal quantum number. This quantum number describes the energy level an electron occupies. The principal quantum number is assigned a positive integer starting with 1. Generally speaking, the larger the number, the further from the nucleus and the higher energy level an electron has. For example, an electron for which n=2 has a higher energy than that of one for which n=1.
Quantum numbers are also used to describe the shapes of orbitals. The second quantum number is represented by the letter (cursive)l.
Values for l are often represented as letters rather than numbers. The lowest energy orbital in each energy level is designated s. It has a spherical shape. (if you missed it earlier, by the way, an orbital is a place where one is likely to find an electron) There is one s orbital allowed in each level. There are 3 p orbitals the p orbitals have greater energy than s orbitals within a specific level. p orbitals are shaped like a dumbell, or two spheres stuck together. There are 5 d orbitals allowed in a level, and 7 f. These have more complex shapes. A third quantum number, the magnetic quantum number, is designated m with a subscript curive l(we?ll call it ml) the value of ml tells you the electrons position by designating the spatial orientation that the electron occupies. Electrons that have the same values of n and l but not necessarily ml are said to be in the same sublevel of the atom. The 2p sublevel contains a maximum of three orbitals, 2px, 2py, and 2pz, oriented on the x, y, and z axis respectively.
To describe the motion of an electron there is a fourth quantum number, m with a subscript s (we?ll call it ms), called the spin quantum number. This value labels the orientation of the electron. Electrons in orbitals spin in opposite directions. These directions are normally designated +1/2 and -1/2.
No two electrons have the same set of four quantum numbers. This statement, first made by german chemist Wolfgang Pauli, is appropriately called the pauli principal. The pauli exclusion principal assures that no more than two electrons can be in the same orbital. There is also a maximum number of electrons in each sublevel and principal energy. You an use the pauli principal along with the four quantum numbers to write the overall electron configuration.

--orbital diagrams and electron configurations are models for electron arrangements--
(ah! the fun part!)
Orbital diagrams or used to show how electrons are distributed within the orbitals and to show direction of spin. In an orbital diagram, each orbital is represented by a box, and the electron is represented as an arrow. The direction of the arrow indicates the direction of spin. Note that there is no compex equation or anything to determine direction of spin, just one arrow up and one arrow down if there are two electrons in the orbital. The orbital diagram for hydrogen, which contains one electron, would be designated as follows:

|^ |
|| |

An electron configuration is an abrieviated form of the orbital diagram. The electron configuration of hydrogen would be 1s^1. (Remember, any time I put a ^ before a number, that means it is a superscript).
How do you write the orbital diagram and electron configuration for boron? Boron has an atomic number of 5, so it has 5 electrons? There are two electrons in the first energy level, both in the s orbital, and three in the second energy level, two in the s orbital and one in the p orbital.

1s^2 2s^2 2p^1

There are several other examples in the book, but I think I got the point across. If you need me to make a couple more examples don?t feel afraid to ask.

Electrons are arranged according to Hund?s rule, which states that electron?s will occupy an open orbital of equal energy before any pairing occurs. In this way, repulsion between electrons in a single orbital is minimized. All electrons in singly occupied orbitals must have the same spin. For ecxample, let?s just say that there are 3 electrons to be put in orbital on on principal energy level 2:

Notice the electrons have all resided in seperate orbitals, and all have the same spin.

You can write electron configurations yourself as long as you keep in mind the maximum number of electrons allowed in each orbital amd the order in which the orbitals are filled. For an atom in the ground state, orbitals are filled beginning with the lowest energy and working to the highest. Here is the layout:

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p

Notice the principal energy levels do not always fill in order. Example, 3d is before 4s, this is because even though 3d is on a lower energy level, it has a higher amount of energy.


chapter three supplement

The modern atomic model

You may have thought of an atom as sort of a miniature solar system. Scientists once thought of the very dense nucleus as the sun, while the electrons equated somewhat to planets. However, the motions of these electrons is now thought to be much more complex.
Quantum theory assigns orbitals to electrons surrounding a nucleus. Each orbital has a charectoristic energy and 3-D shape that shouldn?t be confused with the eliptical orbits of the solar system. The actual way in which electrons move around a nucleus can?t be known. Instead, the quantum mechanical model is conserned with the probability of finding an electron ar a specific point.


The identity of an atom is determined by the number of protons it has, it?s atomic number. If the number of protons changes, it becomes a different element.
In an electricly neutral atom, the number of protons equals the number of electrons. The number of neutral neutrons, however, can vary. In fact, all of the elements occur as two or more isotopes. Isotopes are atoms with the same amount of protons and electrons, but different amount of neutrons.

Finding the amount of neutrons

This is as simple as subtracting the atomic number from the mass number.

Okay these supplements are just repeating what I?ve already spent hours typing, if you have a question just ask and if I can I?ll help.



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Registered: 05/10/01
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Re: The chem book I promised [Re: rommstein2001]
    #1969470 - 10/01/03 02:52 PM (18 years, 26 days ago)

I'll put more up later. Working on chapter four for ya. YEah I got a lot of time onmy hands.


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The Duk Abides

Registered: 05/17/03
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Re: The chem book I promised [Re: rommstein2001]
    #1970592 - 10/01/03 09:52 PM (18 years, 26 days ago)

Hey thanx! I'll copy-n-paste this for my reference library. :smile: 

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