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“Atom.” The word comes from the Greek a-tomos, meaning “indivisible.” At the time these particles were named, scientists thought atoms were the smallest bits of stuff found in nature. We now know differently, but the name stuck.
About 100 different kinds of atoms exist. Most are found in nature. Scientists make others in a laboratory.
Some things, such as gold, lead, and iron, are “pure.” That is, they’re made up of only one kind of atom. Other things, such as plants, wood, and plastic, are made up of a combination of atoms. How atoms are organized and held together determines whether they form an apple, a glass of water, or air in a balloon.
Atoms are always moving, even the atoms that make up solid things like a block of wood. Of course, you can’t see or feel the movement because the atoms are so small and closely packed together.
When you think of atoms, think very small. Many millions of atoms would fit on the head of a pin.
