The electron affinity values are negative for: (A) Be rightarrow Be - (B) N rightarrow N - (C) O rightarrow O 2- (D) Na rightarrow Na - (E) Al rightarrow Al - Choose the most appropriate answer from the options given below:

Chemistry · Periodicity of Elements and Periodic Properties

JEE Main 2024 — 6 April, Shift 1 — Question 70

The electron affinity values are negative for:

(A) $\mathrm{Be \rightarrow Be^-}$

(B) $\mathrm{N \rightarrow N^-}$

(D) $\mathrm{Na \rightarrow Na^-}$

(E) $\mathrm{Al \rightarrow Al^-}$

Choose the most appropriate answer from the options given below:

Option A:
D and E only
Correct
Option B:
A, B, D and E only
Option C:
A and D only
Option D:
A, B and C only

Answer: A

Step-by-step solution

Electron affinity is negative when energy is released on addition of an electron.

(A) $\mathrm{Be \rightarrow Be^-}$ Be has completely filled $2s^2$ configuration. Adding electron enters higher energy $2p$ orbital. Electron affinity is positive (endothermic). Not negative.

(B) $\mathrm{N \rightarrow N^-}$ N has stable half-filled $2p^3$ configuration. Adding electron disturbs stability. Electron affinity is small and positive or not negative.

(C) $\mathrm{O \rightarrow O^{2-}}$ This involves second electron affinity. Adding electron to negatively charged $\mathrm{O^-}$ requires energy. Thus, endothermic and not negative.

(D) $\mathrm{Na \rightarrow Na^-}$ Na gains electron to complete $3s^2 3p^6$ configuration. Energy is released. Electron affinity is negative.

(E) $\mathrm{Al \rightarrow Al^-}$ Addition of electron releases energy. Electron affinity is negative.

Thus, the processes D and E have negative electron affinity.

Answer key and solution verified before publishing.

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Exam: JEE Main 2024
Paper: 6 April, Shift 1
Subject: Chemistry
Chapter: Periodicity of Elements and Periodic Properties
Topic: Periodicity in Chemical Properties (Ionization Energy, Electron Affinity, Electronegativity)