During a chemical reaction, an iron atom became the ion Fe2+. What happened to the iron atom?

The answer is the atom lost electrons

When an atom lost electron, it will obtain a positive charge that caused it transform from Fe into Fe2+

The opposite effect will appear if the atom lost proton, it will obtain a negative charged that will add additional; (-) to the atom. (assuming it's in a same amount, it will be Fe2-)

The Iron atom lost two electrons to become the Fe2 + ion. This is referred to as oxidation.