Chemistry S & P Block Elements MDCAT 2017
PMDC Verified Question 86 of 104
Among the following, which one is least reactive metal:
A
Mg
B
Na
C
Ca
D
Be
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Be
Concept:

The chemical reactivity of s-block metals is directly tied to how easily they lose their valence electrons. This is governed by their Ionization Energy (IE). High IE = low reactivity.

Solution:

  • Reactivity in metals increases down a group and decreases across a period.
  • Among the given options, Beryllium (Be) is located at the very top of Group II-A.
  • Because of its exceptionally small atomic radius, its valence electrons are tightly held by the nucleus, resulting in the highest Ionization Energy among the listed metals.
  • This makes it incredibly difficult for Be to lose electrons, making it the least reactive metal of the group.


Why other options are incorrect:

  • Na: Group I metal, extremely reactive due to large size and low IE.
  • Mg & Ca: Lower down in Group II-A than Be, hence they have larger radii, lower IE, and are much more reactive than Be.

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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