Which of the following represents the correct trend for the mentioned property? Choose the correct answer from the options given below :
- B and C only
- A, B and D only
- A and B only
- A, B, C and D
Answer
(2) A, B and D only
Solution
A. First ionisation enthalpy ( kJ mol-1): F (1681) > P (1012) > S (1000) > B (801). P > S because of the stable half-filled 3p3 configuration. Correct.
B. Electron affinity ( kJ mol-1): Cl (349) > F (328) > S (200) > P (72). F < Cl because of the small size of F (strong electron–electron repulsion). Correct.
C. Metallic character decreases across a period: Mg > Al. The correct order is K > Mg > Al > B. Incorrect.
D. Basic character of oxides decreases with decreasing metallic character: K2O > Na2O > MgO > Al2O3 (Al2O3 is amphoteric). Correct.
A, B and D only.
Answer: (2)