2H₂ + O₂ → 2H₂O

This equation shows that:

* 2 molecules of hydrogen gas (H₂) react with 1 molecule of oxygen gas (O₂) to produce 2 molecules of water (H₂O).

It's important to note that this equation represents the synthesis of water, not the "symbol equation of water" itself. Water is a compound, not a reaction.