Skip to content

Elements

Radiation and the atom · level 3, lesson 2 of 6

A question to start

Millions of different things exist: wood, water, glass, salt, skin. Are there millions of kinds of atoms too?

The idea

No. There are only about a hundred kinds of atoms. A substance made of only one kind of atom is called an element.

  • Gold is made only of gold atoms.
  • Oxygen, the gas we breathe, is made only of oxygen atoms.
  • Carbon makes up diamonds and graphite, the black part of pencil lead.
  • Iron makes steel strong and gives Mars its red colour.

118 elements are known. About 90 are found in nature; the rest have only been made in laboratories. Everything else, from water to wood, is made of elements joined together in different ways.

goldoxygencarboniron

Worked examples

1. A gold ring. Pure gold is an element: every atom in it is a gold atom.

2. Diamond and graphite. Both are pure carbon. The atoms are just arranged differently, so one is hard and clear and the other soft and black.

3. Water is not an element. It is made of two kinds of atoms, hydrogen and oxygen, joined together.

Try it

  1. What is an element?
  2. About how many elements are found in nature?
  3. Diamond and graphite are both made of which element?
  4. Is salt an element? (It is made of sodium and chlorine.)
Answers
  1. A substance made of only one kind of atom.
  2. About 90.
  3. Carbon.
  4. No, it has two kinds of atoms.

Common mistake

"Air is an element." Air is a mixture of several elements and compounds: mostly nitrogen and oxygen, with some argon and carbon dioxide.

Where it leads