An alkali metal (A) belongs to period number II and group number I react with oxygen to form (B). (A) reacts with water to form (C) with liberation of hydrogen compound Identify A, B, C.

Explanation

An alkali metal (A) belongs to period number II and group number I is lithium.
(ii) Lithium reacts with oxygen to form simple oxide lithium oxide (B)
`4Li + O_(2) tounderset("Lithium oxide")( 2Li_(2)O)`
(iii) Lithium reacts with water to form lithium hydroxide with liberation of hydrogen
` 2Li + 2H_(2)O to underset("Lithium hydroxide ")(2LiOH) + H_(2)`Lithium directly react with carbon to form an ionic compound lithium carbide.
` 2Li + 2C to underset("Lithium carbide")(Li_(2)C_(2))`Lithium    Li
Lithium oxide    ` Li_(2)O`
Lithium hydroxide     `LiOH`
Lithium carbide     `Li_(2)C_(2)`(kindly insert a table)