Chemistry Solids SZABMU 2023
PMDC Verified Question 21 of 54
Which of the following solids have strong metallic bond?
A
Potassium
B
Phosphorus
C
Calcium
D
Sulphur
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Calcium
Concept:
Metallic bond strength depends on two main factors: a smaller atomic radius and a larger number of delocalized valence electrons.

Solution:
  • First, Phosphorus (P) and Sulphur (S) are non-metals; they form covalent molecular solids, not metallic bonds. This eliminates B and D.
  • We compare the two remaining metals: Potassium (Group 1) and Calcium (Group 2).
  • Calcium provides two valence electrons per atom to the electron sea, whereas Potassium provides only one.
  • Additionally, Calcium has a smaller atomic radius and a higher effective nuclear charge compared to Potassium.
  • The combination of more mobile electrons and a smaller ionic core results in a significantly stronger electrostatic attraction in Calcium.


Why other options are incorrect:
  • A: Potassium has fewer valence electrons and a larger size, making its metallic bond weaker (evident by its much lower melting point).

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