The electron affinity values are negative for Choose the most appropriate answer from the options given below :
- A, B, D and E only
- D and E only
- A and D only
- A, B and C only
Answer
(4) A, B and C only
Solution
Electron affinity = energy released when an electron is added ⇒ it is negative when energy is absorbed
A: Be 2s2 (full) ⇒ e- must enter 2p ⇒ energy absorbed ⇒ A is negative
B: N 2p3 (half-filled, stable) ⇒ energy absorbed ⇒ B is negative
C: O- + e- O2- needs a lot of energy (repulsion by O-) ⇒ overall absorbed ⇒ C is negative
D: Na 3s1 3s2 ⇒ energy released ⇒ D is positive
E: Al 3p1 3p2 ⇒ energy released ⇒ E is positive
∴ A, B and C only
Answer: (4)
Note: The official NTA answer key gives option (2). Our faculty team has re-checked this question and finds option (4) correct, as explained above.