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What are atoms?

Over two thousand years ago, about 400 B.C., the Greek philosopher Democritus tried to figure out what the world is made up of and how it came to be the way it is. He came to the conclusion that all things are made up of tiny particles, too small to be seen. There are many kinds, he thought, and they are always moving about, sometimes combining, and sometimes separating again.

Democritus deserves tremendous credit for giving us this theory.

In the past people believed in many ideas which new knowledge and experience later proved false1. But all the discoveries of science in over two thousand years of work and study show that Democritus was right.

Investigations by chemists have shown that every chemical compound, such as salt or water, is made up of many tiny particles called molecules. In solids and liquids they are packed closely together. In gases they are spread out thin, with big spaces separating the molecules from each other. Each molecule in a compound is the same as all the other molecules in the same compound, but it is different from the molecules in other compounds. Since there are thousands of different compounds, there are thousands of different kinds of molecules, ranging from simple ones, like the molecules of salt or water, to very complicated ones found only in living things.

Further study has shown that the molecules themselves are made up of still smaller particles known as atoms. Although there are thousands of different molecules, there are only 103 different kinds of atoms. These 103 different kinds of atoms, known as the chemical elements, are the building blocks out of which all material things are made.

(From The Outline of Man's Knowledge by Clement Wood)


1) What is the world made up of according to Democritus?

2) Did his theory prove right?

3) When and where did Democritus live?

4) What is every chemical compound made up of according to modern science?


1. proved false - оказались ошибочными

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