Chemistry

Today is 25 July 2010. Students, the scores on the Mass Balance test were very low.

It is obvious that you need more practice in balancing chemical reactions as well.  I will provide more opportunity to practice, although it is up to you to actually apply the opportunity.

The questions that required you to provide input from your lab is another story.  If you won't do the work and won't write down the data from your experiments, there is a problem.  As I reviewed the lab reports, I saw that most students did not bother writing a report for the experiment.  Even worse, many students did not even write down the results from weighing the samples at various stages.  How much effort, really, is involved in weighing an empty beaker, weighing it after burning a strip of magnesium and weighing it after you reacted an acid with the MgO, and evaporated the liquid?  You were instructed to count drops to get to an end point; you were taught how to convert the number of drops to milliliters, and you were shown that the molarity of the acid was 1 M.  All of this you were taught.  At every step of the way, I asked for questions.  At every step you were given a chance to demonstrate understanding.  What happened between the instruction and the exam? 

High school is supposed to be rigorous.  (If you don't know the meaning of "rigorous," look it up in a dictionary!)  Your teachers are not supposed to give you crayons and paper and limit your education to making pretty pictures.  Chemistry class requires you to study material presented and to complete assignments.  You need 60% of the available points to pass the class.  Right now, most of you are not passing and, in most cases, it is because you have not turned in assignments.  Remember, 30% of the grade is based on lab reports, 30% on tests, 30% on classwork and 10% on homework.  A student can fail all of the exams and still pass the class if they do the other assignments.  What, really, is the big problem?

--Jay L. Stern

Today is 18 July 2010 -- Science students, scientists, engineers, doctors, nurses, geologists and business men or women are just some of people who need to write reports, essays and descriptions of things important in their lives.  

Today, I will teach you to write a simple essay using chemical equilibrium as related to oxygenation of living tissue.  In this way I link chemistry to biology!

First, think of three things relating equilibrium and oxygenation of tissue.

1.  Forward rate equals reverse rate

2.  Animal tissues need oxygen

3.  Animal tissues need carbon dioxide removed

Second, write a sentence for each of the "things."  These are called "topic sentences." 

1.  Chemical equilibrium is when the forward rate of a chemical reaction equals the reverse rate. 

2.  Animal tissues need oxygen for the survival of the organism.

3.  Carbon dioxide is produced as the oxygen combines with carbon produced from foods. 

Third, write sentences which support the topic sentence like this:

Chemical equilibrium is when the forward rate of a chemical reaction equals the reverse rate. The reactions occur at the same time.  One reaction goes one direction; the other reaction goes the other direction.  The reactions are the opposite of each other.  The rates are in balance with each other. 

Animal tissues need oxygen for the survival of the organism.  They get the oxygen from the blood which transports it.  The blood picks up the oxygen in the lungs of land animals, and from the gills of aquatic animals.  Iron in the blood is what binds to the oxygen.  It holds the oxygen until the blood moves to a place in the body where the concentration of oxygen is low.  Then the oxygen is released to the tissue.

Carbon dioxide is produced as the oxygen combines with carbon produced from foods.  This carbon dioxide needs to be removed from the body.  It does so by exchanging with the oxygen.  As the oxygen is released from the red blood cells, the carbon dioxide binds.   This causes the concentration of carbon dioxide to be greater than the concentration in the air.  When the blood circulates to the lungs, it is released because the oxygen from the air displaces it. 

Fourth, write an introduction to this essay and a conclusion which wraps things up.  Briefly cover the three points which you describe in the three paragraphs for the introduction and summarize or highlight them in the conclusion.  

Here are some samples for you to use in preparing essays on other topics we have covered in my various courses (chemistry, biology, environmental science, integrated and coordinated science):

1.  How is equilibrium involved in manufacturing chemical products (examples; Haber process, production of various salts)?

2.  What are the differences between the three, basic types of rock?

3.  Is global climate change caused by human activity?

4.  Why are significant figures and scientific notation useful in scientific work

-- Jay L. Stern

Today is 11 March 2010 -- Here is the algebraic method of balancing chemical reactions.  

EXAMPLE:   Balance NaHCO₃ + CH₃COOH --> CO₂ ^ + H₂O + CH₃COONa using the algebraic method.

Step 1:  Place letter coefficients in front of each term.

a NaHCO₃ +  b CH₃COOH -->  c CO₂ ^ + d H₂O +  e CH₃COONa

Step 2:  Write equations for each element using the letter coefficients to balance.  Remember that the subscripts indicate how many of the preceding atom there are in the formula.

Na:  a = e

  H:  a + 4b = 2d + 3e

  C:  a + 2b = c + 2e

  O:  3a + 2b = 2c + d + 2e

Step 3:  Note that we have five unknowns, but only 4 equations.  We want the same number of equations as unknowns.  Start by substituting "a" for "e."

Thus: a + 4b = 2d + 3(a)

          a + 2b = c + 2(a)

         3a + 2b = 2c + d + 2(a)

Simplify:  4b = 2d + 2a

Divide by 2 to yield 2b = d + a

Also, 2b = c + a

And, 2b = 2c + d - a

Since 2b = d + a = c + a, then
d + a = c + a, and c = d

Similarly, 2b = c + a = 2c + d - a so  -c + a = d - a, or -c + 2a = d

Substitute "c" for "d" to yield -c + 2a = c.  Therefore 2a = 2c and a = c.

Step 4:  Make an assumption.  Assume that "a" has a value of "1."  You can let it have any value you want, but "1" is simplest. 

Then:  a = 1 and c =1

           Since a = e, then e = 1

           Since c = d, then d =1

Solve for "b" in any of the equations:  b = (c + a) / 2 or (1 + 1) / 2 = 1

So all the coefficients are 1 and the equation balances.

Study this method.  The keys are (1) writing separate equations for each element, (2) Simplifying and substituting to obtain one equation for each unknown, and (3) make a simplifying assumption, (4) check for mass balance.

          

Now, you practice.  If you can balance the following equations by sight or trial-and-error, go for it.  Otherwise, use the algebraic method to balance the following equations:

1.  Fe + H₂SO₄ --> Fe₂(SO₄)₃ + H₂ ^

2.  KOH + H₃PO₄ --> K₃PO₄ + H₂O

3.  C₂H₆ + O₂ --> H₂O + CO₂

4.  SnO₂ + H₂ --> Sn + H₂O

5.  NH₃ + O₂ --> NO + H₂O

6.  KNO₃ + H₂CO₃ --> K₂CO₃ + HNO₃

7.  B₂Br₆ + HNO₃ --> B(NO₃)₃ + HBr

8.  BF₃ + Li₂SO₃ --> B₂(SO₃)₃ + LiF

9.  (NH₄)₃PO₄ + Pb(NO₃)₄ --> Pb₃(PO₄)₄ + NH₄NO₃

10.  SeCl₆ + O₂ --> SeO₂ + Cl₂

Today is 15 November 2008 --- Math is the language of science

Until you speak "Math," you will have great trouble in understanding science.  And, you need science to graduate from high school, not to mention how useful it is in everything that matters to you in your world. 

We covered simple fractions, percentages, decimal fractions and how to rearrange equations to solve for unknown variables.  I have even listed a You-Tube link that shows how to rearrange equations.  I urge you to go to this link (below) and watch the video.

Here are some simple steps to rearranging an equation to solve for an unknown.

1.  Collect similar terms (i.e. -- all the known values on one side; the unknown that you are trying to solve for is on the other side of the equal sign.)

2.  What you do to one side of the equation, you do to the other side. 

3.  If you are adding, then you subtract the term from both sides; if you are multiplying, then you divide, and so on.

Look at this example:

P1x V1 / T1 = P2x V2 / T2

This is the "combined gas law."  It tells you that the pressure times the volume of a gas divided by the temperature is always equal to a constant value.  The pressure times the volume divided by the temperature for the same gas at a different set of conditions must also equal the constant.  Therefore, the two conditions can be set equal to each other.  If the temperature has not changed, then T1 = T2 and they cancel out.  That leaves P1 x V1 = P2 x V2.  Let us say you know the initial pressure, P1, the initial volume V1, and the final pressure P2.  Then we need to rearrange to solve for the new volume, V2.  Let's see how:

P1 x V1 = P2 x V2

(P1 x V1 )/ P2 = (P2 x V2)/ P2

Since we are multiplying P2, we divide it to enable us to move it to the other side of the equation.  The P2 in the numerator cancels with the P2 in the denominator on the right side.  Rewriting:

P1 x V1 /  P2 = V2

In words, "P1 times V1 divided by P2 equals V2."

If you knew the initial volume, the initial pressure and the final pressure, and you needed to find the final volume, you would rearrange the equation to find V2.  Practice these relationships for a while and you will see how easy this becomes.

Today is 18 February 2008 -- Of Students and Assessments

Have you heard the expression, "Teach to the Test?" It means a teacher will attempt to cram into a student's head the answers to questions that will most likely to be on an assessment exam. Teaching to the test does not give students the deep background necessary to really understand a topic. It does not do much more than help them select the "right" answer from a set of multiple choice answers. So why do teachers teach to the test? Usually, it is because we are on tight schedules and have little alternative. What we can do is to provide our students with background material which fills in the gaps that we cannot cover in class. Basically, the answers to the assessment questions are in the material I am providing in these Class Notes, but you have to search for them! In doing so, your understanding is bound to increase and you probably will achieve a higher score on the assessment tests than by not studying the notes.

Some students believe the test is something to be ridiculed. They don’t even bother to read the questions; just use a pencil to darken in circle A, B, C or D as an answer for each question. What are the consequences of this behavior? For sure, it lowers the academic standing of the school. But it hurts them, too. The fact is, students who do well on assessment tests generally do better in life. Why anyone deliberately wants to fail is something I don’t understand.

The test rules don’t let teachers remove the test papers from these young people. We are supposed to simply collect the papers and have them scored. Yet, there is something that can be done. We teachers can monitor our students during the exam. If it seems like someone is just filling in the answer sheet without studying the questions – without trying to do the best they can – then I can “out” them. I can post a list of their names, the reason why they are on the list and the basis for the reason. I can contact parents and counselors, and I will.

On the flip side of this particular coin is another choice: Students can study the material presented and pay attention in class. They can complete their homework assignments and not goof off in class. Then, they can answer the assessment questions to the best of their ability and they will see that they are, indeed, quite able.

Let’s get started. In chemistry, the periodic table is THE central thought. It is more than just a chart hanging on a wall. The table lists the known elements in the order of increasing protons. Protons are particles in the nucleus of every atom of every element. Hydrogen has one proton and it’s atomic number is one. Uranium has 92 protons and its atomic number is 92. Do you see how this works?

Sometimes students confuse atomic number with “atomic mass.” Atomic mass is the sum of the mass of the protons AND the neutrons in an atom’s nucleus. Neutrons are neutral particles; they have no charge. Protons are about the same mass as neutrons, but they have a positive charge. To find the number of neutrons, subtract the atomic number – the number of protons – from the atomic mass. The difference is the number of neutrons.

What balances the charge on the protons? Electrons do. These are particles of very low mass, compared to a proton. In fact the mass of an electron is said to be 1/1730 of the mass of a proton. They carry a negative charge that is exactly equal to and opposite of the charge on the proton. The protons and neutrons are in the nucleus of the atom; the electron is some distance away from the nucleus. People like to think of the atom as a tiny solar system with the nucleus at the center, like the sun, with the electrons orbiting the nucleus like planets. It is not a totally accurate model, but it works. Importantly, it does imply that most of the mass of the atom is contained in the nucleus, just as most of the mass of our solar system is contained in our sun. Since the balance of the atom is mostly empty space, can you imagine how dense the nucleus must be?

Actually, the density of the nucleus has been calculated. The radius of the nucleus is estimated as between 1/10,000 to 1/100,000 the radius of the whole atom. The mass is about 10–24 grams. Doing the math suggests that the density of the nucleus is about 1015 grams per cubic centimeter.

Let’s put this into units you are more accustomed to. There are 453.59237 grams in a pound. There are 28,316.8466 cubic centimeters in one cubic foot. Doing the math (1015 g/cc) x (28,316.85 cc/cu. ft.) / (1lb/453.59 g) = 6.24 x 1016 lb/cu. ft. The density of water is 62.34-lb/cu ft. so the nucleus is 10,014,163,340,000,000 times as dense as water.

I mentioned that the periodic table is the central thought in chemistry. It was not always so. In the time of the Ancient Greeks, thinkers were already trying to understand the world around them. They came up with the idea that there were four elements – that is, four basic substances that made up everything about them. These four were earth, wind, fire and water. It is easy to see why they thought this: When something was burned, it produced ash, which certainly resembled the earth upon which they walked. And water appeared to be in bodily fluids, fruits and other liquids. Wind was the air they breathed and fire, why it was literally the stuff of life. Even the ideas of the philosopher Democritus, who said that all matter was composed of finite elements that he called “atomus,” did not conflict with the concept of four, basic substances.

But the concept of an element as a unique substance did not seem to have occurred to the Greeks, nor to people for thousands of years. They headed down the wrong path of science, trying to “transmute” common metals into gold, for example. To them, this exercise in futility made perfect sense. If there were only four elements, then proper blending of various substances that contained the elements should produce the desired result. It never did. But what the early experimenters did accomplish was to build up a body of knowledge of what did not work. Further, they discovered how to isolate various substances and what the properties of those substances were.

The man who brought some order to the confusion was John Dalton. In 1802 he published work that has come to be known as “Dalton’s Atomic Theory.” There were five main points: -Elements are made of tiny particles called atoms. -All atoms of a given element are identical. -The atoms of a given element are different from those of any other element; the atoms of different elements can be distinguished from one another by their respective relative weights. -Atoms of one element can combine with atoms of other elements to form compounds; a given compound always has the same relative numbers of types of atoms. -Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process; a chemical reaction simply changes the way atoms are grouped together. Although portions of Dalton’s work has been modified based on later discoveries, his ideas serve as a guide to chemistry even today. For example, we retain the idea that elements are the smallest part of a substance that retains its unique properties. Of course, John Dalton knew nothing of subatomic particles, isotopes or radioactive decay. Nevertheless, his ideas served as a roadmap for later scientists, taking them off of the dead-end path originally charted by the Greeks.

By the time of Demetri Mendelev in the 1880’s, then a young professor of chemistry in Russia, quite a lot about the various elements had been learned. Mendelev was the first to organize them into a pattern that recognized the repeating nature of the elements. That is, various elements – while unique – shared properties with other elements. For example, Sodium and Potassium reacted similarly with Fluorine or Chlorine. Mendelev placed these elements in rows and columns that reinforced their similarities. The rows were called “periods,” and the columns were groups or “families.” Sodium and Potassium were placed in the same family based upon their similar reaction with water. They made compounds long known to be alkaline, or basic. Further, they were observed to be metals so the family has been named the ”alkali metals.” The next column contains the similar elements Magnesium and Calcium. They also are metallic and produced alkaline substances. They were given the name “alkaline earth metals” in recognition of the ancient Greek concept of “earth,” the origin of many compounds containing calcium and magnesium.

Fluorine and Chlorine form salts with most metals, especially the alkali metals and alkaline earth metals. The Greek root for salt is “halo,” and the notion of formation is in the root “gen.” Therefore this family, which includes Bromine, Iodine and Astintine, is named “Halogen” for “salt-former.” Notably, the elements in this family are gaseous or solid at room temperature. They lack the malleability, sheen and electrical conductivity of metals and are therefore “nonmetals.”

At the time of Mendelev, the inert or “Noble Gas” family was not known. These are elements that usually do not enter into chemical reaction. The reason has to do with their atomic structure. They include Helium, Argon, Neon, Krypton, Xenon and Radon and are traditionally listed to the right of the Halogen family on the periodic table.

If you examine a modern periodic table, you will see the various groups and families. A zig-zag line on the right side of the table divides the semi-metals or “metalloids” and the non metals from the metals. Isn’t it amazing that so many of the elements are metals? Beside the groups mentioned above, we have the “transition metals,” including gold, iron, zinc and manganese as examples. We also have the “lanthanide” series and “actinide series.” The elements in these series follow Lanthanum and Actinium respectively. They are usually listed in two rows below the main table and their position indicated by lines.

When you examine the periodic table, you observe that the atomic mass is not a whole number. Chromium, for example, has a mass listed on the periodic table in your text of 51.9961. Even Carbon, the basis of the table, has a mass of 12.0107, not 12.0000. How can this be? It is so if some atoms of the element have more or fewer neutrons than the vast majority of the atoms for that element. When the weight of the element is determined, the mass of the individual atoms is totaled and divided by the number of atoms. This gives the average mass. Practically, it is done by percentages. For example there are four known forms or “isotopes” of chromium. These are 50Cr, 52Cr, 53Cr and 54Cr. There is one form, 51Cr, that has been made in the laboratory, but it has such a short life that we do not consider it here. It is not believed to occur naturally. The atomic number of Chromium is 24, which means it has 24 protons and there are 26, 28, 29 and 30 neutrons respectively in the naturally occurring isotopes. Analysis of samples of Chromium show that there is 4.345% of 50Cr, 83.675% of 52Cr, 9.501% of 53Cr and 2.365% of 54Cr. We can find the average weight by converting percentages of each to the decimal form, multiplying by the mass of each isotope and adding the result together:

(0.04345)(50) + (0.83675)(52) + (0.09501)(53) + (0.02365)(54) = 51.9961

This shows you that the atomic mass listed on the periodic table is an “average.”

The metalloids, by the way, exhibit some properties of metals. For example, they are somewhat electrically conductive and find use in – of course – semiconductors in the electronic industry. In fact, transistors and modern computers as we know them would be impossible with out these elements.

As you examine the modern periodic table, you will probably marvel at its organization. For example, patterns and trends are there for all to see. Beside the periodic nature of the table and the way the atomic mass increases, the reactivity in terms of electronegativity becomes apparent as does atomic radius and ionic radius. For example, the atomic radius increases as you go down a column, or family. This is intuitive since additional electron orbitals are a characteristic of each, subsequent period of the table, and those orbitals increase the radius. Less obvious is how the atomic radius decreases as you move left to right across a period. This is a result of the increasing number of protons in the nucleus attracting and holding more tightly the electrons in the orbitals. The ionic radius – that is, the radius when an electron has been gained or lost – is not quite as intuitive. While it makes sense for the ionic radius of metals to decrease because protons are added left to right, but not additional layers of electrons, what about for the non metals? The radius of these ions – anions – also tends to decrease because of the increasing protons in the nucleus. This appears to be true even though electrons are added to the outermost shell.

Because of the tendency of the elements to react – their electronegativity – Linus Pauling made a scale to show this. Fluorine, the most electronegative element was assigned the value of 4 on his scale. All other elements were rated based on it. Francium, in the lower left hand corner of the table, is least electronegative (0.7 on the Pauling scale). All elements have electronegativity between these two limits.

Previously, I wrote that the ideas of the Greeks drove early chemists down a dead-end path. I also wrote that they still found much along that path which was useful to later generations of investigators. These pioneers learned that some substances were denser than others; that is, equal volumes contained greater mass than others. Comparing their density was one way that counterfeit gold coins could be detected. They learned that “like dissolves like,” such as when salt dissolves in water but not in oil. They also found that different substances had different melting and boiling temperatures. Why would this be so? Clearly, it is a function of some property of the atom or – where atoms have joined together – of molecules, but what? Thinking about it, we realize that different amounts of energy – as heat – are needed to melt or boil the substance. The difference must reflect the amount of energy between the atoms or molecules holding them together: the stronger the interatomic or intermolecular forces, the higher the melting or boiling point.

Dalton’s realization that the same weight of one element might react with different weights of two other elements was the forerunner of the “mole concept.” This term, from the Latin term for “mass, massive structure,” is used to describe the number of combining units of a substance available for a reaction. It is based on the amount of the substance, typically in grams, and the atomic mass, referenced to carbon-12. Therefore it is a “made-up” definition, much as one dozen means 12 of something, like “a dozen eggs.” What might make for some confusion to the student is the fact that beside showing the relation between a mass and an atomic mass, the mole also is defined in terms of Avogadro’s number, 6.02 x 1023.

Let’s explore these concepts in a little more depth. First, understand that our system of measurement is based on the arbitrary assignment to Hydrogen of a mass of “1 atomic mass units” or “amu.” That is, it has a single proton to which a mass of 1 has been assigned. If there are intelligent beings elsewhere in the universe, they may have assigned hydrogen a different mass. However, regardless of the absolute mass, it would be so anywhere in the universe that what we named “carbon-12” has 6 protons and 6 neutrons. The mass ratio of carbon-12 to hydrogen will always be 12:1, regardless of the mass assigned by any of the “locals.” Notice that I am not including any isotopes – about which we will speak soon – of either hydrogen or carbon in this discussion. In this system, if we take one gram of hydrogen and divide by the atomic mass of hydrogen – 1 amu – our answer is 1 mole. If we have 12 grams of carbon-12 and we divide by the atomic mass of carbon-12 – 12 amu – we have 1 mole. The same is true for any element from Helium to Lawrencium.

Now here is the interesting part: In one mole of Hydrogen, there are 6.02 x 1023 atoms of Hydrogen. In 1 mole of Carbon-12 there are – you guessed it -- 6.02 x 1023 atoms of carbon-12. So the mole is a short-hand way of taking the mass of the substance out of the equation and just considering the way atoms interact with each other based on their number. Let’s look at it as a mathematical expression:

6.02 x 1023 atoms = 1 mole = mass (grams) / atomic mass (amu)

Here is an example: You have 24.000 grams of carbon-12. The atomic weight of carbon-12 is defined as 12.000 amu. Dividing 24.000 by 12.000 is 2. Therefore, there are 2 moles of carbon-12 in 24.000 grams of carbon-12. Further, since 1 mole contains 6.02 x 1023 atoms of carbon-12, there are 1.20 x 1024 atoms of carbon-12 present in 2 moles. When John Dalton noted that atoms could combine with each other to form various compounds, he could not have known that combining required interaction of electrons. It took work by early 20th century investigators such as J.J. Thompson, Gilbert Lewis and Irving Langmuir, to name just a few, to understand that there were several ways in which atoms could bond to each other, all involving what are called “valence electrons.” These are the electrons in the outermost orbital of an atom. With elements that have very few electrons in their outermost orbital, it is most easy for them to be “donated” to elements whose atoms need but few electrons to fill their outer orbital. Thus, even if the individual atoms then contain more or fewer protons than are balanced by the remaining number of electrons, the atoms are “stable.” That is, the electron shells that remain are complete. Atoms in this condition are called “ions.” They are named “Cations” and are positive when they have lost electrons and so have more protons than electrons. They are named “Anions” and are negative when they have gained electrons so there are fewer protons than electrons. Of course, the atoms are always found in a compound of two or more elements, so the charge on one is balanced by the opposite charge on another atom. For example, you cannot reach into a bowl of salt water and pluck out an individual sodium ion, leaving behind an unmated chloride ion.

The term “electronegativity” is used to describe the tendency of atoms of elements with different numbers of valence electrons to react with each other. Atoms of elements with one valence electron, for example, are highly reactive with atoms of elements that just need one electron to complete their outer shell. This is why alkali metals and halogens are so reactive; one wants to donate its electron and the other wants to accept it. Bonds formed in this manner are termed “ionic.” Compounds which display ionic bonding are always composed of a metal and non metal. They conduct electricity in solution, and form crystalline structures, not discrete molecules.

Another class of bonding is termed “covalent.” This type of bonding involves atoms of similar or identical electronegativities. Rather than donate and receive electrons between atoms, the valence electrons are shared between atoms. This is sort of like a child who spends some of the time with one parent and the rest of the time with the other. Each parent can claim the child as their own, just as each atom can claim it has a full outer shell of electrons --- at least part of the time. Examples of covalent bonding include atoms of halogens reacting with each other to form molecules such as F2 or Cl2 (Fluorine gas and Chlorine gas, respectively). As you can see, there is a total difference between an element in its “atomic” form (Cl) and its “molecular” form (Cl2).

The third major type of bonding is called “metallic.” In metallic bonding, electrons are delocalized; they “belong to all” of the atoms in a sample of the substance. Not surprisingly, metallic bonding give metals their properties of heat and electrical conductivity.

Regardless of the type of bonding, it is often useful to look at HOW the atoms are bonded together. This gives an idea of the reactivity of the compound – or of the atom. Gilbert Lewis devised a method called “dot-diagrams” specifically to help chemistry students visualize bonding arrangements. The diagrams used the elements letter symbols with dots around them to show bonding to neighboring atoms and the number of bonds. For example, elemental carbon has four valence electrons; hydrogen has but one. To complete its outer orbital, could carbon donate its four electrons to hydrogen, or gain another four from four hydrogen atoms? This does not happen because the electronegativities of both elements are similar so the atoms share electrons. The dot diagram shows this:

H

..

H: C : H

,,

H

In this diagram, the hydrogen atoms have two electrons; one each of their own and one that they share with carbon. And the carbon has eight electrons which completes its outer shell, four of which were its own and the other four shared with the four Hydrogen atoms. This diagram also illustrates the “octet rule” which states that (most) atoms need 8 electrons to fill their outer shell and be stable. The formula for this compound – methane – is CH4 by the way.

Today is 11 February 2008 -- Please use the hyperlink to read the editorial by Gerald F. Wheeler, Executive Director of the National Science Teachers Association

Mr. Wheeler's editorial mirrors my thoughts on science education.  Please read the editorial and let your parents read it.  Education today is too important NOT to have full participation by all people involved.  That means you, the student; me, the educatior; the administrators and -- very, very important -- your parents.  One thing you can do after you have read the editorial is to send me your thoughts on how I can best teach you the science that you need to compete in this world. 

Today is 28 September 2007 --  PRESS ON! 

Students, I rarely ask you to memorize anything word-for-word.  "Press On!" is one of those rare times.  Calvin Coolidge, known as "Silent Cal," the 30th president of the United States (1872 - 1933) was known as a man of few words.  The story is told how at a diplomatic reception, a young woman said to him that she bet her friend that she could get Mr. Coolidge to say more than three words.  The president is reputed to have replied, "You lose."  But when he DID speak, his words are worth noting.  Please memorize "Press On!" completely.  I will ask you to write it out from memory on an upcoming quiz:

"Nothing in the world can take the place of Persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent. The slogan 'Press On' has solved and always will solve the problems of the human race."