Question 9
What is the chemical formula of magnesium nitride?
The right answer is the one marked above.
Mg3N2. Magnesium has a valency of 2 and nitrogen a valency of 3, so crossing over puts 3 on the magnesium and 2 on the nitrogen.
This compound is real, and you have met it before: metals such as magnesium react with nitrogen gas when heated, forming the nitride of the metal.