Chemistry Chemical Bonding NUMS 2019
PMDC Verified Question 77 of 102
The shielding effect of inner electron is responsible for:
A
Decreasing ionization energy
B
Having no effect on ionization energy
C
Increasing ionization energy
D
Increasing electronegativity
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Decreasing ionization energy
Concept:

Shielding effect occurs when inner shell electrons repel outer shell electrons, partially blocking the attractive pull of the positive nucleus.

Formula:

$$ Z_{\text{eff}} = Z - S $$

Solution:

  • As the number of inner electron shells increases (moving down a group), the shielding effect becomes stronger.


  • This reduces the effective nuclear charge (\( Z_{\text{eff}} \)) felt by the outermost valence electrons.


  • Because they are held less tightly, less energy is required to remove them, resulting in a decreased ionization energy.


Why other options are incorrect:

  • Option C & Option D: Shielding makes electrons easier to lose, which decreases ionization energy and electronegativity, rather than increasing them.

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.

Previous Question All Chemical Bonding MCQs Next Question

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.

Enter Arena Sprint iOS App Android App