Question: can the oxidation state of an element be fractional

Answer: Yes, Fractional oxidation states are often used to represent the average oxidation state of several atoms of the same element in a structure. For example, the formula of magnetite is Fe O , implying an average oxidation state for iron of +8/3. However, this average value may not be representative if the atoms are not equivalent. In a Fe O crystal below 120 K (−153 °C), two-thirds of the cations are Fe and one-third are Fe , and the formula may be more specifically represented as FeO Fe O .