Lithium (Li) is a metallic chemical element with atomic number 3. It is the lightest of all solid elements.

Lithium belongs to a group of highly reactive elements called Alkali Metals, together with sodium, potassium, rubidium, caesium and francium.

There are two common isotopes of Lithium, ⁶Li and ⁷Li, of which ⁷Li is the more abundant one.