Chemistry S & P Block Elements SZABMU 2023
PMDC Verified Question 32 of 104
Which element has smaller shielding effect among the following?
A
Mg
B
Ca
C
Rb
D
Sr
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Mg
Concept:

The shielding (or screening) effect is caused by the inner electron shells repelling the valence electrons. The fewer the inner shells, the smaller the shielding effect.

Solution:

  • To find the element with the smallest shielding effect, we must identify the element with the fewest electron shells (lowest period number).
  • Let's locate the options on the periodic table:
    Mg: Period 3 (2 inner shells shielding).
    Ca: Period 4 (3 inner shells shielding).
    Sr & Rb: Period 5 (4 inner shells shielding).
  • Because Magnesium (Mg) has the fewest occupied electron shells, its valence electrons experience the smallest shielding effect.


Why other options are incorrect:

  • Ca, Sr, and Rb are in lower periods, meaning they possess more principal quantum shells, significantly increasing the shielding effect.

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 S & P Block Elements 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