A compound forms whenever two or more atoms form chemical bonds with each other. The chemical formula for water is H2O, which means each molecule of water consists of one oxygen atom chemically bonded to two hydrogen atoms.
The characteristics that proves water to be a compound are
1. Water doesnot retains the characteristics of its constituent elements . Hydrogen is a gaseous combustible gas and oxygen is a gas supporter of combustion whereas water is a liquid that supports neither combustion nor is combustible
2.The two elements are combining in fixed ratio.
3. Its contituents cannot be seperated by physical means like filtration e.t.c but can be by chemical means , Electrolysis