Chemistry S & P Block Elements UHS 2024
PMDC Verified Question 1 of 104
The difference of lithium from the other alkali metals is mainly because of:
A
Large radius and low charge density
B
Large radius and high charge density
C
Small radius and low charge density
D
Small radius and high charge density
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Small radius and high charge density
Concept:

Anomalous behavior in the first member of a group is driven by its highly concentrated positive charge.

Solution:

  • Lithium sits at the very top of Group 1, meaning it has the fewest electron shells.
  • Consequently, its atomic and ionic radii are exceptionally small compared to the rest of the alkali metals.
  • Because this small size is carrying a +1 charge, the charge is concentrated in a tiny volume. This is mathematically defined as a high charge density.
  • This intense charge density allows \( \text{Li}^+ \) to strongly distort (polarize) the electron clouds of anions, granting covalent character to its bonds—a trait completely unlike the rest of the highly ionic Group 1 metals.


Why other options are incorrect:

  • Lithium has the smallest radius, not the largest. Its charge density is inherently high due to this small volume, not low.

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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