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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3pn124

Which of the following statements is/are correct?

  1. AThe first ionisation enthalpy of N is higher than that of O.
  2. BThe electron gain enthalpy of O is more negative than that of S.
  3. CAtomic radii of group 15 increase in the order N < P < As < Sb < Bi.
  4. DThe first ionisation enthalpy of P is higher than that of S.

Answer: A, C, D

Radius increases as shells are added. N has a half-filled stable 2p3 configuration and P a half-filled 3p3 configuration, so each has a higher ionisation enthalpy than its group 16 neighbour. Oxygen has a less negative electron gain enthalpy than sulphur because of electron repulsion in the compact 2p subshell, so the last statement is false.
Practice p-Block Elements: Groups 15 and 16 More on Trends in groups 15 and 16
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