Chemistry S & P Block Elements PMC 2021
PMDC Verified Question 62 of 104
Addition of second electron to a uni-negative ion always ____?
A
An endothermic process
B
An exothermic process
C
Neutral process
D
Energy wasted
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: An endothermic process
Concept:

Electron affinity is the energy change when an electron is added to an atom. While the first electron addition is usually energetically favorable, subsequent additions are not.

Solution:

  • When the first electron is added to a neutral atom (like Oxygen), energy is released (exothermic process) because the nucleus pulls the electron in. The atom becomes a uni-negative ion (\( \text{O}^- \)).
  • When you try to force a second electron into this already negative ion, the incoming electron experiences severe electrostatic repulsion from the existing electron cloud.
  • To overcome this massive repulsion, energy must be forcefully supplied from an outside source.
  • Because energy must be absorbed to force the electron in, the second electron affinity is always an endothermic process.


Why other options are incorrect:

  • It is impossible for it to be exothermic (Option B) because a negative charge will naturally repel another negative charge without the input of external energy.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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