Mg + O2 > MgO balancing

Explanation:

The law of conservation of mass states that in a chemical reaction, the mass of the reactants must be equal to the mass of the product.

Practically speaking, this means that in a chemical reaction, the number of atoms of each element in the products must be equal to the number of atoms of the same elements in the reactants.

Here we have the following chemical reaction:

We observe that this reaction is not balanced, because:

- There is 1 atom of magnesium in the reactants and 1 atom of magnesium in the products

- There are 2 atoms of oxygen in the reactants and only 1 atom of oxygen in the products

In order to balance, we add a coefficient of 2 to the product:

Now the oxygen is balanced, but the magnesium is not; therefore, we add a 2 on the atom of magnesium in the reactants:

Now the reaction is balanced.