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What happens when calcium metal reacts with oxygen in air?

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A labeled diagram of the periodic table entry for calcium, showing its atomic number 20, symbol Ca, atomic weight 40.078, electron configuration, and classification as an alkaline-earth metal. Icons indicate calcium is a solid with a face-centered cubic crystal structure and strongly basic oxides at room temperature. — calcium The chemical element calcium is the most abundant metallic element in the human body.

When calcium metal is exposed to air, it reacts slowly with oxygen, water vapour, and nitrogen to form a yellow coating consisting of oxide, hydroxide, and nitride.1

If the metal is burned in air or pure oxygen, it reacts to form calcium oxide.1