Chemistry Chemical Bonding UHS 2022
PMDC Verified Question 38 of 102
Which of the following element has smaller size?
A
Na
B
Al
C
K
D
Li
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Li
Concept:

Atomic radius decreases left to right across a period (due to increasing nuclear charge) and increases top to bottom down a group (due to adding new electron shells).

Formula:

$$ \text{Size Trend: Top Right} < \text{Bottom Left} $$

Solution:

  • Lithium (Li) is in Period 2.


  • Sodium (Na), Aluminum (Al), and Potassium (K) are in Period 3 and Period 4.


  • Because Li only has 2 electron shells, while the others have 3 or 4, Li possesses the smallest atomic radius among the given options.


Why other options are incorrect:

  • Option A, Option B, Option C: All have more principal quantum shells than Lithium, inherently making them substantially larger.

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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