Question

Pr, Nd, Tb and Dy exhibit +4 oxidation state only in oxides of type MO₂. Why?

Answer 1

Usually all Pr, Nd, Tb and Dy lanthanide tends to show stable oxidation state of +3. Now, if these lanthanide tends to form + 4 oxidation state that will be unstable. Thus, to stabilise the +4 oxidation state of these lanthanide a strong electronegative elements is required to remove the 4th electron and which will not allow these lanthanide to accept electrons again to form +3 oxidation state. Since oxygen is the most electronegative element after fluorine. Hence + 4 oxidation state is most stable with oxygen only i.e Pr, Nd, Tb and Dy exhibit +4 oxidation state only in oxides of type MO₂