Chemistry S & P Block Elements MDCAT 2017
PMDC Verified Question 84 of 104
The following sketch shows the melting point of eight elements with consecutive atomic numbers. Which element is silicon?

C
A
A
B
C
C
B
D
D
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: C
Concept:

In Period 3, the melting point of elements increases up to Group IVA (Silicon) due to the formation of a strong, giant covalent network, and then sharply drops.

Solution:

  • The graph displays a peak at a specific point.
  • Silicon (Si) forms a giant three-dimensional covalent lattice, giving it the highest melting point in the third period.
  • On the given graph, this maximum peak is labeled as point C.
  • Therefore, point C represents Silicon. (Note: In the historical options layout, Option B corresponds to the label 'C' on the graph.)


Why other options are incorrect:

  • Points A, B, and D correspond to elements with weaker metallic bonding or simple molecular structures, leading to lower melting points.

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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