Question

Give example and suggest the reason for the following:

(i) The lowest oxide of transition metal is basic, the highest is acidic.
(ii) A transition metal exhibits higher oxidation states in oxides and fluorides.
(iii) The highest oxidation state is exhibited in oxo anion of a metal.

Answer 1

(i) The lower oxide of a transition metal is basic because the metal atom has a low oxidation state whereas the highest oxide is acidic due to a higher oxidation state for example, MnO is basic while Mn₂O₇ is acidic.

(ii) A transition metal exhibits a higher oxidation state in oxides and fluorides because oxygen and fluorine are highly electro negative elements, small in size (and strongest oxidising agents). For example, osmium shows an oxidation state of +6 in O₅F₆ and vanadium shows an oxidation state of +5 in V₂O₅.

(iii) Oxo metal anion have the highest oxidations state, eg: Cr in Cr₂O₇^-2, has an oxidation state of +6, whereas Mn in MnO₄^– ion has an oxidation state of +7. This again due to the combination of the metal with oxygen which is a highly electronegative and oxidising element.