Question

Which of the following arrangements does not represent the correct order of the property stated against it?

• A. $V^{2+}<C{r}^{2+}<M{n}^{2+}<F{e}^{2+}$: paramagnetic behaviour
• B. $N{i}^{2+}<C{o}^{2+}<F{e}^{2+}<M{n}^{2+}$ : ionic size
• C. $C{o}^{3+}<F{e}^{3+}<C{r}^{3+}<S{c}^{3+}$ : stability in aqueous solution
• D. $Sc<Ti<Cr<Mn$ . number of oxidation states

Answer 1

Answer: (A)

(a) $V^{2+}=3$ unpaired electrons
$C{r}^{2+}=4$ unpaired electrons
$M{n}^{2+}=5$ unpaired electrons
$F{e}^{2+}=4$ unpaired electrons
Hence, the order of paramagnetic behaviour should be
$V^{2+}<C{r}^{2+}=F{e}^{2+}<M{n}^{2+}$
(b) Ionic size decreases from left to right in the same period
(c) (As per data from NCERT)
$C{o}^{3+}/C{o}^{2+}=1.97;$
$F{e}^{3+}/F{e}^{2+}=0.77;$
$C{r}^{3+}/C{r}^{2+}=-0.41;$
$S{c}^{3+}$ is highly stable (It does not show $+2$).
(d) The oxidation states increases as we go from group $3$ to group $7$ in the same period.