Question

What is the chemical formula for calcium oxide?

Answer 1

The formula for calcium oxide is CaO.

Explanation:

Calcium oxide is an ionic compound composed of the metal calcium and nonmetal oxygen.

Calcium is an alkali earth metal (group 2/IIA). The atoms of the alkali earth metals have two valence electrons, which they lose when forming ions. Therefore, calcium cations have a charge of `2^+`.

Oxygen is in group 16/VIA and the atoms of all elements in this group have six valence electrons, and need two more to have an octet and become stable. Therefore, oxide anions have a charge of `2^(-)`.

The overall charge of an ionic compound is zero. Since the charges of the calcium and oxide ions are equal but opposite, the calcium and oxide ions form a `1:1` ratio `(2^+ + 2^(-)=0)`, and the chemical formula is `"CaO"`.