Identify the correct statements from the following.
Identify the correct statements from the following.
$A, B$ only
$A, C$ only
$B, C$ only
$A, B, C$
Solution
( Alkali metals are strong reducing agents because after the removal of the only valence electron $\left(n s^1\right)$ they can gain the electronic configuration of noble gases $(n-1) p^6$, that is more stable electronic configuration.
$\mathrm{KO}_2$ is paramagnetic oxide due to the presence of 1 unpaired electrons. The number of electrons present is 17 where the sixteen electrons are from two oxygen atoms and one from the negative charge $\left(\mathrm{O}_2^{-}\right)$. Its molecular orbital configuration can be written as
$
\begin{aligned}
& \sigma 1 s^2 \sigma * 1 s^2 \sigma 2 s^2 \sigma * 2 s^2 \sigma 2 p_z^2 \pi 2 p_x^2=\pi 2 p_y^2 \pi * 2 p_x^2 \\
&=\pi * 2 p_y^1 \sigma * 2 p_z^0 .
\end{aligned}
$
So, statement (B) is worng.
The hydration enthalpies of alkali metal ions decrease with increase in ionic sizes.
$
\mathrm{Li}^{+}>\mathrm{Na}^{+}>\mathrm{K}^{+}>\mathrm{Rb}^{+}
$
$\mathrm{Li}^{+}$has maximum degree of hydration and for this reason, lithium salts are mostly hydrated, e.g. $\mathrm{LiCl} \cdot 2 \mathrm{H}_2 \mathrm{O}$