The given chemical equation is balanced. It shows that two molecules of hydrogen gas (H2) react with one molecule of oxygen gas (O2) to produce two molecules of water (H2O). The number of atoms of each element is the same on both sides of the equation.

H2 + O2 → 2H2O

2 atoms H 2 atoms H 4 atoms H

1 atom O 2 atoms O 2 atoms O