Water is a compound composed of two elements, Hydrogen and Oxygen. Each water molecule consists of two Hydrogen atoms joined chemically with an Oxygen molecule. We write the formula for water as H2O.
The scientific name for water is hydrogen oxide.
We can use symbols and a formula to show this chemical reaction:
2H2 + O2 ⇒ 2H2O
When we write an equation we have to balance it. The number of atoms must remain equal on both sides of the arrow. The number of atoms in the reactants is the same as in the products.