Question

Arrange the following in increasing order of electron affinity: (A) F, (B) Cl, (C) Br, (D) I, (E) At

• A. B $>$ A $>$ C $>$ D $>$ E
• B. A $>$ B $>$ C $>$ D $>$ E
• C. B $>$ C $>$ A $>$ D $>$ E
• D. B $>$ A $>$ C $>$ E $>$ D

Hint:

Chlorine is the "Electron Affinity King" of the periodic table because it lacks the tiny-atom repulsions found in Fluorine.

Answer 1

The Correct Option is A

Step 1: Concept Electron affinity is the energy change when an electron is added to a neutral gaseous atom. Generally, it decreases down a group as atomic size increases.

Step 2: Meaning For halogens (Group 17), the expected trend is F $>$ Cl $>$ Br $>$ I $>$ At. However, there is a known anomaly between Fluorine and Chlorine.

Step 3: Analysis Fluorine has a very small atomic size, leading to high inter-electronic repulsions in its $2p$ subshell. This makes the addition of an incoming electron less favorable compared to Chlorine, which has a larger $3p$ subshell to accommodate the electron.

Step 4: Conclusion Chlorine has the highest electron affinity in the group. The corrected order is Cl $>$ F $>$ Br $>$ I $>$ At, which corresponds to B $>$ A $>$ C $>$ D $>$ E. Final Answer: (A)