Both alkali metals and alkaline earth metals are `s-`block elements. They resemble each other in many respects but still there are certain dissimilarities in their properties due to different number of electrons in the valence shell, different atomic radii, ionisation enthalpy, electronegativity, etc.
Like lithium, Be also differs from rest of the alkaline earth metals on account of its small atomic size and high electronetativity. `Be^(2+)`ion is very small and exerts a high polarising effect on any anion associated with it.
The correct sequence of increasing covalent character is

Options

A. `BeCI_(2) lt NaCl lt LiCl`
B. `NaCl lt LiCl lt BeCl_(2)`
C. `BeCl_(2) lt LiCl lt NaCl`
D. `LiCl lt NaCl lt BeCl_(2)`

Answer

B

Explanation

Charge/radius ratio order: `Na^(o+) lt Li^(o+) lt Be^(2+)` Polarising ability: `Na^(o+) lt Li^(o+)lt Be^(2+)`
Covalent character: `NaCl lt LiCl lt BeCl_(2)`