Atoms and molecules
Atoms Elements Water molecule
Atoms are the tiny pieces of matter that make up everything. You are made of atoms too.
Atoms are the smallest part of an element, which are too small to see. Even the strongest microscopes cannot show a single atom. If 7 billion people on earth were as small as an atom, they would fit in less than 1mm of space.
An element is a substance that is made of only one kind of atom. Everything in the universe has atoms of one or more elements. The atoms in an element are all the same, but they are different from the atoms in other elements. There are 118 different elements. They are shown on the periodic table. Some examples of elements are oxygen, hydrogen and carbon.
Molecules Molecules are groups of two or more atoms that are joined by chemical bonds. Atoms from different elements can mix. When the atoms are from different elements, the molecule is also a compound.
Some elements like helium do not make bonds. Helium atoms are single atoms.
Some elements like hydrogen, nitrogen and oxygen make molecules with two atoms of the same element.
Water is made of molecules. Each water molecule has two hydrogen atoms and one oxygen atom that are bonded together. This means that water’s chemical formula is H2O.
Carbon dioxide is made of molecules with one carbon atom and two oxygen atoms (CO2).
Single element molecules Oxygen molecule
Some molecules are made of only one kind of atom. This means the molecule is also an element. Oxygen is an element that is not a metal. It is found naturally as a molecule. Each molecule has two oxygen atoms that are bonded strongly together. Oxygen is a gas at room temperature. A picture of two red circles joined together. An oxygen molecule An oxygen molecule always has two atoms in it.
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