The balanced chemical equation when sodium and oxygen react is as below
4 Na + O₂ → 2 Na₂O
Explanation
From equation above 4 moles of sodium (Na) react with 1 mole of oxygen (O₂) to produce sodium oxide ( Na₂O)
Since there is equal number number of atoms in side of reactants and in the side of product the equation is balanced.
For example there is 4 atoms of Na in side of reactant and 4 in side of product.
