Question

Which of the following is/are correct representation of the property stated against it?

• A. $V^{2+}<T{i}^{2+}<M{n}^{2+}<F{e}^{2+}:\text{Magnetic moment}$
• B. $N{i}^{2+}<C{o}^{2+}<F{e}^{2+}<M{n}^{2+}:\text{Ionic size}$
• C. $C{o}^{3+}<F{e}^{3+}<C{r}^{3+}<S{c}^{3+}:\text{Stability in aqueous solution}$
• D. $V{O}_2^{+}<C{r}_2{O}_7^{2-}<Mn{O}_4^{-}:\text{Increasing oxidising power}$

Answer 1

Answer: (B), (D)

The correct options are
B $N{i}^{2+}<C{o}^{2+}<F{e}^{2+}<M{n}^{2+}:\text{Ionic size}$
D $V{O}_2^{+}<C{r}_2{O}_7^{2-}<Mn{O}_4^{-}:\text{Increasing oxidising power}$

(a) $\text{Magnetic moment}\propto n$
Since, magnetic moment $=\sqrt{n(n+2)}$, where $n$ is number of unpaired electron.
$n$ for $V^{2+},T{i}^{2+},M{n}^{2+}$ and $F{e}^{2+}$ is 3, 2, 5 and 4.
So the correct order be: $T{i}^{2+}<V^{2+}<F{e}^{2+}<M{n}^{2+}:\text{Magnetic moment}$

(b) For transition metals, the radii of the cation having same charge decreases from left to right in the same period.

(c) Stability of the transition metal in aqueous solution is directly proportional to the number of unpaired electrons. The half filled and completley filled d-orbitals are extra stable.
$[Co{]}^{3+}=3d^6-1\text{unpaired electron}$
$[Cr{]}^{3+}=3d^3-3\text{unpaired electron}$
$[Fe{]}^{3+}=3d^5-5\text{unpaired electron}$
$[Sc{]}^{3+}=[Ar]-\text{inert gas configuration}$
So the order becomes:
$C{o}^{3+}<C{r}^{3+}<F{e}^{3+}<S{c}^{3+}:\text{Stability in aqueous solution}$

(d) Oxidising power is the tendency to accept an electron. $V^{+5},C{r}^{+6}$ and $M{n}^{+7}$ has the same electronic configuration. As the effective nuclear charge increases, oxidising power also increases.