The combining power of magnesium and oxygen is the same, i.e. 2. What will be the molecular formula of magnesium oxide ?

1. Mg₂O₂
2. MgO₂
3. Mg₂O
4. MgO

MgO

Reason — The combining power of magnesium and oxygen is the same, i.e. 2.

$\overset{\phantom{2}{2}}{\text{Mg}} \space {\swarrow}\mathllap{\searrow} \space \overset{2}{\text{O}} \Rightarrow \underset{\phantom{2}{2}}{\text{Mg}} \space {\swarrow}\mathllap{\searrow} \underset{\phantom{2}{2}}{\text{O}} \\[1em] \text{Mg}$2\text{O}2 \Rightarrow \text{Mg}\text{O}

When the subscript numbers are same, we don't write them. So, the molecular formula of magnesium oxide is MgO.