Iron 26 is not stable in its ground state of
The valance electrons
or by losing the two
Oxygen is a strong oxidizer it will take the electrons from the Iron resulting in Oxygen having a negative two charge (-2)
One equation for the Oxidation of Iron is below ( there are more than this possibility)
the three Oxygen atoms that have been adding for every two Iron atoms add 48 grams to the compound. This increases the mass of the compound over the original mass of the Iron.