Balancing iron and oxygen into iron oxide

In this video, we balance the reaction between iron and oxygen.

Here is question one. Balance: F e plus O two yields F e two O three.

You are given iron reacting with oxygen to form iron oxide. We need the smallest whole-number coefficients that conserve every element. Initially, iron has one atom on the left and two on the right.

Oxygen has two atoms on the left and three on the right. Change coefficients only, because changing subscripts would change the substances. First, balance oxygen using six atoms, the least common multiple of two and three.

Put three before oxygen and two before iron oxide. Now oxygen has six atoms on each side, but iron has one on the left and four on the right. Put four before iron to balance those four iron atoms.

Check both elements: each side now has four iron atoms and six oxygen atoms. The coefficients have no common factor, so they are the smallest whole numbers. The balanced equation is four F e plus three O two yields two F e two O three.