Part 2

Every single thing in the world is made of atoms. Atoms are so tiny that there are only a few microscopes in the whole world powerful enough to show them. It would take about 20 million atoms to make a dot as big as this one over the letter i. In fact, if you had one atom for every single person in the states of Pennsylvania and California, you could fit them all on the head of a pin!

But, small as they are, atoms are the building blocks that make everything. You certainly don't look anything like an elephant--do you? But you are both made of atoms! You don't look anything like a scrambled egg, either--or a washcloth, or a refrigerator--but they are all made of atoms, too!

Atoms are everywhere, they are everything--and you should learn something about them because you live in the atomic age.

Why is this the atomic age? Were atoms just discovered? No, they weren't. People have known about atoms for a long time.

Then what is different about this age? The difference that we have learned how to make atoms work for us. We call this work atomic energy.

When your father and mother were children, no one had ever heard of atomic energy. Energy for heat, light, and to operate machinery came from a few main sources. Some came from water power, a little from wind power--but almost all energy came from burning fuels.

The chief fuels of the world for many years have been coal, oil, and natural gas. These are all fossil fuels. That means that they were made millions of years ago and have lain trapped in the earth ever since. Once these fuels are used up, there will be no way to replace them. There just won't be any more.

By the early years of the 1900's, some people were beginning to worry about fuel. There wasn't any shortage yet, and there wouldn't be for a long time. There were still new coal mines and new oil wells being discovered. But some day, the last one would be discovered, the fuels would be all used--and then what?

As new industries developed all over the world, the need for power grew--and so did the worry. And then suddenly, in 1942, one of the greatest discoveries of all time was made. The atomic age was born and the perfect fuel was found.

Atomic energy can do things never before dreamed of. Atoms, without any fire, without any noise, can run a huge electricity plant. The atoms in one pound of fuel can keep the lights burning in your home for 1000 years!

Atoms can send a large ship back and forth across the ocean many times--on one small load of fuel!

Atoms can keep hamburger fresh for weeks without freezing!

Atoms can sometimes cure sick people!

Atoms can find leaks in pipes, and can test the rubber in a set of car tires!

Atoms, in many ways, can make life easier, healthier, and better for us.

What are these wonderful atoms, anyway? Let's find out.

THE SMALLEST THING THERE IS

The story of atoms begins about two thousand years ago, in ancient Greece. There, a wise man named Democritus started to think about what things were made of. Democritus reasoned that you could take a little piece of anything at all--wood, metal, even candy--and cut it in half. Then you could cut the halves in half. Then you could cut those pieces in half. And so on. But finally, Democritus said, you would get to particles so tiny that they could not be divided any more. He called these smallest particles atoms, from the Greek word atomos which means indivisible.

It was hard for people to believe that everything in the world was made of atoms. They soon forgot about Democritus and his strange ideas. Atoms were forgotten for almost two thousand years.

But during the eighteenth century, European scientists again became interested in the structure of things and began to experiment. There were some curious discoveries.

Chemists found that a substance like water could be separated into two other substances, hydrogen and oxygen. But hydrogen and oxygen couldn't be broken down into any other chemicals no matter what the chemists did. They could easily change table salt into sodium and chlorine. But no matter how hard they tried, they weren't able to break down sodium and chlorine into anything else.

So scientists decided that most of the things around us--water, salt, wood, animals--were made of combinations of substances. They called the combinations chemical compounds. They called the substances that couldn't be broken down elements.

We now know of more than one hundred elements. In the year 1800, about half that number had been discovered. And it was at about this time that an Englishman, John Dalton, came along with the first really scientific atomic theory.

Dalton said that all elements are made of atoms, and the atoms of any particular element are always the same. An atom of carbon is always like every other atom of carbon. And, Dalton went on, atoms of different elements have different weights. An atom of carbon weighs more than an atom of hydrogen. An atom of oxygen weighs more than an atom of carbon.

Dalton noticed that atoms combined in different ways according to their weights. Water is made of hydrogen and oxygen. But it takes two hydrogen atoms with one oxygen atom to make water. This smallest unit of water is called a molecule. A molecule is the smallest possible amount of any chemical compound.

Another contribution that Dalton made was the use of shorthand symbols to stand for chemical elements. Today, we use a system which grew out of Dalton's.

Instead of calling the water molecule "two atoms of hydrogen and one atom of oxygen," we call hydrogen "H" and oxygen "O" and write, simply, H{2}O. The symbol for carbon is "C" and carbon dioxide may be written CO{2}. This means that one carbon atom and two oxygen atoms combine to form one molecule of carbon dioxide.

John Dalton was a great scientist and almost everything in his atomic theory turned out to be correct. Only one of his ideas we now know to be wrong. And that idea went all the way back to Democritus. They both thought that the atom was the smallest possible particle, and that it could never be divided.