Question

Give examples and suggest reasons for the following features of the transition metal chemistry:

(i) The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.

(ii) A transition metal exhibits highest oxidation state in oxides and fluorides.

(iii) The highest oxidation state is exhibited in oxoanions of a metal.

Answer 1

(i) $M{n}^{\left(II\right)}O$ is basic and $M{n}_2^{\left(VII\right)}{O}_7$ is acidic.

$C{r}^{\left(II\right)}O$ is basic and $C{r}_2^{\left(III\right)}{O}_3$ is amphoteric.

The ions in lower oxidation state can readily donate electrons and acts as bases and the ions in high oxidation states have a tendency to accept electrons and act as an acid.

(ii) Small sized (and highly electronegative) oxygen and fluorine can readily oxidize the metals. For example, $O{s}^{\left(VI\right)}{F}_6$ and $V_2^{\left(VI\right)}{O}_5$.

(iii) Due to high electronegativity and high oxidizing power of oxygen, metal oxoanions have highest oxidation state. For example, In dichromate ion, $Cr$ has $+6$ oxidation state and in permanganate ion, $Mn$ has $+7$ oxidation state.