Atoms and Molecules — Reading Comprehension Lesson

Reading Passage

Atoms and Molecules

Everything around you — your desk, your pencil, the air you breathe, even your own body — is made of tiny particles called atoms. Atoms are the basic building blocks of all matter in the universe. They are so small that millions of them could fit on the head of a pin.

Although atoms are extremely tiny, they are made of even smaller parts called subatomic particles. The center of an atom is called the nucleus. The nucleus is made of two kinds of particles: protons, which have a positive electrical charge, and neutrons, which have no charge at all.

Tiny particles called electrons move around the nucleus in what scientists picture as cloud-like layers. Electrons have a negative charge. The number of electrons in an atom usually matches the number of protons, which keeps the atom electrically balanced.

An element is a substance made of only one type of atom. Hydrogen, oxygen, gold, and iron are all examples of elements. Each element has its own special number of protons. There are over 100 known elements, and they are organized on a chart called the periodic table.

When two or more atoms join together, they form a molecule. A water molecule, for example, is made of two hydrogen atoms and one oxygen atom — that is why water is sometimes called H2O. Atoms can combine in countless different ways to form all the materials we see, from sugar and salt to plastic and metal.

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