Question

$ZnC{O}_3$ is thermally more stable than $MgC{O}_3$ because:

• A. $Mg(OH{)}_2$ exhibits only basic properties while $Zn(OH{)}_2$ is amphoteric
• B. polarising action of $Z{n}^{2+}$ with 18-electron configuration on the anion is larger than that of $M{g}^{2+}$ with a noble-gas electron configuration and of same size and charge.
• C. both (a) and (b) are correct
• D. none of the above is correct

Answer 1

The correct option is B polarising action of $Z{n}^{2+}$ with 18-electron configuration on the anion is larger than that of $M{g}^{2+}$ with a noble-gas electron configuration and of same size and charge.

$ZnC{O}_3$ is thermally more stable than $MgC{O}_3$ because polarising action of $Z{n}^{2+}$ with 18-electron configuration on the anion is larger than that of $M{g}^{2+}$ with a noble-gas electron configuration and of same size and charge. Higher is the polarizing power, higher will be the lattice enthalpy and higher will be the thermal stability.