Which of the following orders are correct regarding their covalent character? i. $\mathrm{KF} \lt…
Which of the following orders are correct regarding their covalent character?
i. $\mathrm{KF} \lt \mathrm{KI}$
ii. $\mathrm{LiF} \lt \mathrm{KF}$
iii. $\mathrm{SnCl}_2 \lt \mathrm{SnCl}_4$
iv. $\mathrm{NaCl} \lt \mathrm{CuCl}$ The correct option is
i, ii, iii only
ii, iii, iv only
i, iii, iv only
i, ii, iv only
Solution
According to Fajan rule, for covalent character, cation should be small in size and should have high positive charge and anion should be large in size and contain high negative charge.
(i) Iodine have more size than $\mathrm{F}^{-}$so, $\mathrm{KI}\gt\mathrm{KF}$
(ii) $\mathrm{K}^{+}$have more size the $\mathrm{Li}^{+}$so, $\mathrm{LiF}\gt\mathrm{KF}$
(iii) $\mathrm{Sn}^{2+}$ and $\mathrm{Sn}^{4+}$
$\mathrm{Sn}^{4+}$ carry more charge than $\mathrm{Sn}^{2+}$
$\text { so, } \mathrm{SnCl}_4\gt\mathrm{SnCl}_2$
(iv) $\mathrm{Cu}^{+}$have pseudo configuration so it has more covalent character than NaCl .
$\mathrm{CuCl}\gt\mathrm{NaCl}$
$\therefore$ (i), (iii) and (iv) are correct