Answer:
2Mg + O2 = Reactant | 2MgO = Product
Explanation:
It is pretty simple, look:
The elements that are being added (or in the majority of the cases, the one who are in the left side) are always the Reactant.
The other side is the product of the reactants.
It is like a mathematic formula
We some the numbers to get the result, the numbers are the reactants and the result is the product.
(I hope you didn´t get confused)
