Essay 8

The atomic (1) theory of matter was held as a philosophic theory by the ancient Greeks, about 2400 years ago. They "considered that the endless variety of substances known to man can be explained if matter is assumed to be composed of small indivisible and indestructible particles, or atoms." (Encyclopedia Britannica, 1948)
The first real scientific advancement came with John Dalton (1766-1844) who defined an atom as the smallest component of a substance that has the physical properties of the substance. This explained many experiments and opened the door to real science. How small a bit of iron (or mercury, or any other element) exhibited the physical properties of that element? The answer was one atom. Two or a thousand or one million atoms of mercury are still mercury and behave the same as half as much or twice as much.
There are ninety-some elements known to occur here naturally. They have names such as Hydrogen, Helium, Lithium, Beryllium Boron, Carbon, Nitrogen, Oxygen, Fluorine, Neon, Sodium, Magnesium, Chlorine, Nickel, Iron, Tin, Tungsten, Uranium, Calcium, Zinc and many others. There is an arrangement called the Periodic Table that shows the repeating patterns among these different elements.
Elements can combine in certain proportions with each other. Two atoms of Hydrogen can combine with one of Oxygen to make something we call water. Combinations of atoms are called molecules. One molecule is the smallest amount of any substance made of a combination of atoms that has the same physical properties as a larger collection of those molecules.
Molecules are reasonably stable combinations of atoms, but absolutes are unachievable and so under severe stress things decompose. A molecule of Methane (natural gas) can, if it is hot enough (burns) combine with Oxygen in a chemical reaction that liberates energy. Methane has one atom of carbon and four of Hydrogen. The molecule looks like this---

into water H-O-H and Carbon Dioxide O=C=O

Notice that Carbon has four bonds (where it connects to another atom) available, Hydrogen has one bond available and Oxygen has two bonds available. Notice that no atoms are gained or lost in the reaction:

Oxygen has two bonds available but [O] is really unstable by itself and so Oxygen gas exists in the atmosphere of this planet as O2 or O=O . Hydrogen gas is similarly unstable by itself and so Hydrogen gas is H-H or H2 .
The fact that these atoms combine with each other in certain proportions---because they have 1, 2, 3, 4, 5, 6, or 7 bonds available---was discovered by Dalton---and named by him the Law of Definite Proportions.

1. from the Greek atomos meaning INDIVISIBLE
The atmosphere of this planet is about 21% Oxygen, 78% Nitrogen, 1/2% Carbon Dioxide and small amounts of other gasses.
It took about another hundred years for a few guys (Werner Heisenberg, Nils Bohr, Albert Einstein, etc., etc.) to work out WHY atoms only combined with other atoms in certain definite proportions and what these things by which they held onto each other, these things called bonds, actually were.

Biology The study of molecules
such as are found in living things
and how they work together

Chemistry The study of atoms and how they
combine to make molecules

Physics The study of matter and how
it behaves and of what it is made

At this point the study moved from the realm of chemistry into the realm of physics. It turns out that atoms, while they were thought to be indivisible, are themselves made of components.

'Tis said that fleas
have smaller fleas
upon their backs
to bite 'em
and these in turn
have smaller fleas
and so on, ad infinitem (2).

The simplest atom is the Hydrogen atom. It has one fairly heavy lump of mass in the middle and a little bitty thing orbiting around it. If that atom were as big as a football field, the lump of mass in the middle would be the size of a housefly.
The lump of mass is not much mass---it takes about 100,000,000,000,000,000,000,000,000 of them to make a pound. The little bitty mass orbiting around the center is much smaller---it takes 1,836 of them to add up to one of the bigger lumps of mass in the center.
Gravitational forces are completely insignificant on this scale. Gravity is the name given to the force that attracts one mass to another because of their masses and the distance between them. Gravity keeps the earth in orbit around the sun, and the moon in orbit around the earth, and your body stuck to the surface of this planet.
For things as small as atoms to stay together---the little bitty thing is orbiting the great big heavy thing at hundreds of thousands of miles per hour---so fast that physicists are never really sure exactly where it is at any given moment---there must be some other attractive force to balance the centrifugal force felt by the little bitty thing orbiting around the thing in the center.

2) Latin---means "to infinity"
There is a more powerful short-range force that exists in this universe. It seems a very fundamental force although we really do not know a lot about it (we physicists do, however, have some really nifty theories). We call the characteristic associated with the force charge. There are two kinds of charge. We call them positive and negative because they come in equal and opposite characteristics. The forces associated with charge are easily measurable. Opposite kinds of charge attract each other. Like kinds of charge repel each other. The particles that have this quality, charge, can move around. A flow of charged particles is called a current.
The big heavy lump in the middle of an atom is called the nucleus of the atom. In the simplest atom, Hydrogen, the only thing in the nucleus is this lump of mass we talked about earlier. It has a charge which is equal and opposite to the charge of the little bitty thing in orbit around it. Arbitrarily, the thing in the middle got its charge called positive and the little bitty thing got its charge called negative.
The little bitty negatively charged things could (a few of them) be dislodged by rubbing a bit of amber (the hardened tree sap) with some fur or silk. Sometimes there would be a bright flash of light as a spark jumped between the pieces. The word ELECTRIC goes back to Latin electricus, meaning produced from amber by friction, from Middle Latin of amber, from Latin ELECTRUM, meaning amber which was known by the name electrum, from the Greek ELEKTRON, akin to ELEKTOR, meaning BEAMING SUN. So, the little bitty thing with the negative charge is called an electron. The heavy lump in the middle is called a proton, from the Greek proton, the neuter gender version of protos, meaning first, and Greek pro- meaning before.
All the other elements have in the nucleus not only protons but some proton-electron pairs stuck together. Opposite charges attract, and the electron can actually go inside the proton and get stuck there. A nucleus may contain some of these combination units as well as plain protons. A combination unit has mass but no net charge (The proton and the electron have equal and opposite charges so one of each adds up to zero.) and since it is electrically neutral it got named a neutron.
That's pretty much what matter seems to be made of.

Copyright c 2002 Steve Smith all rights reserved