Final answer:
The correct balanced chemical equation for Na + O2 → Na2O is 4Na(s) + O2(g) → 2Na2O(s), ensuring the same number of each type of atom on both sides of the equation following the law of conservation of matter.
Step-by-step explanation:
To balance the chemical equation Na + O2 → Na2O, we need to consider the rule that diatomic molecules such as O2 exist as two atoms when they are not combined with other elements. We need to ensure that the number of atoms for each element is equal on both sides of the equation.
We see that O2 has two oxygen atoms, but Na2O has only one oxygen in the formula. Therefore, we need to balance the oxygen atoms by multiplying Na2O by two, which gives us 2Na + O2 → 2Na2O. This still isn't balanced because now we have four sodium atoms on the product side and only one on the reactant side. So, we add a coefficient of 4 in front of Na on the reactant side, resulting in the final balanced equation:
4Na(s) + O2(g) → 2Na2O(s)
Each element now has the same number of atoms on both sides of the equation, satisfying the law of conservation of matter.