Atom Rearrangement

Choose Reaction

2H₂ + O₂ → 2H₂O
Hydrogen combustion CH₄ + 2O₂ → CO₂ + 2H₂O
Methane combustion N₂ + 3H₂ → 2NH₃
Haber process 2Mg + O₂ → 2MgO
Metal combustion

Atoms are never created or destroyed, the same atoms appear on both sides, just rearranged. This is Lavoisier's Law of Conservation of Mass.