Question

In which of the following arrangements the order is NOT according to the property indicated against it ?

• A. Al3+< Mg2+< Na+< F– – increasing ionic size
• B. B < C < N < O – increasing first ionisation enthalpy
• C. I < Br < F <Cl – increasing electron gain enthalpy (with negative sign)
• D. Li < Na < K <Rb – increasing metallic radius

Answer 1

Answer: (B)

B < C < N < O – increasing first ionisation enthalpy

Answer 2

Nitrogen has half filled stable configuration, ns2np3. So, ionization enthalpy of nitrogen is greater than oxygen. On moving down the group, metallic radius increases due to increase in number of shells.