Question

The ion which shows maximum value of hydration energy is:

• A. ${Li}^{+}$
• B. $K^{+}$
• C. ${Na}^{+}$
• D. ${Cs}^{+}$

Answer 1

The correct option is A ${Li}^{+}$

The ion which shows the maximum value of hydration energy is $L{i}^{+}$.
The size of the alkali metal cation determines the degree of hydration. Small sized cations have greater charge density and greater tendency to draw electrons from molecules which are thus polarised. Among alkali metals, $L{i}^{+}$ ion is the most extensively hydrated. $C{s}^{+}$ ion is the largest alkali metal ion and is least hydrated. The decreasing order of the relative degree of hydration is
$L{i}^{+}>N{a}^{+}>K^{+}>R{b}^{+}>C{s}^{+}$.