Question

Write the formula for an ionic compound formed from O^2- with each of the following ions. Magnesium ion sodium ion aluminum ion

Answer 1

Oxygen oxidation number -2, Magenisium oxidation number +2. So the compound magenisium oxide having formula MgO (+2-2=0).

Oxygen oxidation number -2, sodium oxidation number +1. So to balance the oxidation of oxygen two sodium atoms (2x+1= +2) are needed. So sodium oxide molecular formula Na₂O (+2-2=0).

Aluminium oxidation number is +3 and oxygen oxidation number -2. So the molecular formula aluminium oxide Al₂O₃.

Al₂ = +3 x 2 . = . + 6

O₃ . = -2 x 3 = . -6

Al₂O₃ = +6-6 = 0.