Question

Which of these ions is expected to be coloured in aqueous solution? $I. Fe^{3+}$ $II. Ni^{2+}$ $III. Al^{3+}$

• A. $I$ and $II$
• B. $II$ and $III$
• C. $I$ and $III$
• D. $I, II$ and $III$

Answer 1

Answer: (A)

$I$ and $II$

Answer 2

$4$ unpaired electrons,
$\therefore$ Coloured ion

$2$ unpaired electrons,
$\therefore$ Coloured ion
$III. Al^{3+}=[Ne]$
No unpaired electron in $3d$, thus colourless ion.