Final answer:
When magnesium burns in air, it can react with nitrogen, after forming magnesium oxide, to create magnesium nitride. The reaction is 3Mg + N2 -> Mg3N2.
Step-by-step explanation:
The reaction equation where Mg₃N₂ is formed when magnesium (Mg) burns in air is as follows:
3Mg(s) + N₂(g) → Mg₃N₂(s)
When magnesium is exposed to the air, it reacts not only with the oxygen present in the air to form magnesium oxide (MgO), but it can also react with nitrogen to form magnesium nitride (Mg₃N₂). However, typically magnesium first burns in oxygen from the air to form magnesium oxide, and then the MgO can react further with nitrogen if the temperature is high enough to drive this reaction forming Mg₃N₂.
The complete reaction process is:
- Magnesium burns in air, primarily reacting with oxygen to form magnesium oxide (2Mg + O₂ → 2MgO).
- After the formation of the magnesium oxide, it can react with nitrogen in the air to form magnesium nitride (3MgO + N₂ → Mg₃N₂ + 3/2O₂).
The overall reaction when magnesium burns in air to form magnesium nitride is a combination of the two steps mentioned above. The presence of nitrogen in the air is required for Mg₃N₂ to form.