Question

Property of the alkaline earth metals that increases with their atomic number is:

• A. Ionisation energy
• B. Solubility of their hydroxides in water
• C. Solubility of their sulphates in water
• D. Electronegativity

Answer 1

The correct option is B Solubility of their hydroxides in water

(a) As we move down the group, atomic radius increases and also effective nuclear charge on the valence electrons decreases. Thus ionisation energy decreases down the group.

(b) For alkaline earth metal hydroxides down the group the lattice energy decreases but change in hydration is very less. So down the group with increasing atomic number, the solubility of their hydroxides increases.

(c) The solubility of the sulphates decreases down the group because of the decrease of enthalpy of solvation down the group.

(d) Electronegativity also decreases down the group, as the atomic radius increases down the group.