Question

The ionic conductance is least for:

• A. $C{s}^{+}$
• B. $R{b}^{+}$
• C. $K^{+}$
• D. $N{a}^{+}$

Answer 1

Answer: (D)

$N{a}^{+}$

Due to the small size of $N{a}^{+}$ ion, it is heavily hydrated in waters and becomes a large hydrated ion.

Higher the size of hydrated ion, lower is its ionic conductance.

Hence, ionic conductance increases down the group in alkali metals in the order, $N{a}^{+}<K^{+}<R{b}^{+}<C{s}^{+}$.

Therefore, option $D$ is correct.