What is the product when Strontium reacts with Oxygen gas? Strontium Peroxide or Strontium Oxide? Please explain why.?

When oxygen gas is passed over heated strontium, the product is strontium peroxide (SrO₂). Strontium is a reactive metal. When pure oxygen is used, the reaction rate is very fast. There is no time for O₂ molecule to break the O=O double bond to form two oxide ions (O²⁻). Instead, O₂ molecule would form peroxide ion (⁻O–O⁻) without completely break the O=O double bond.

However, when air is passed over heated strontium, the product is a mixture of strontium oxide (SrO) and strontium nitride (Sr₃N₂). Air is a mixture of oxygen and nitrogen, and thus the reaction rate of the reaction is slower that that of using pure oxygen. O₂ molecule has sufficient time to break its O=O double bonds to form two oxide ions. Besides, strontium reacts with nitrogen in air to give strontium nitride.