Why FeO is non-stoichiometric with the formula Fe0.95 O explain?
The non-stoichiometry reflect the ease of oxidation of Fe2+ to Fe3+ effectively replacing a small portion of Fe2+ with two thirds their number of Fe3+. Thus for every three "missing" Fe2+ ions, the crystal contains two Fe3+ ions to balance the charge . i.e. 3Fe2+ = 2Fe3+ to maintain electrical neutrality