Chemistry S & P Block Elements MDCAT 2016
PMDC Verified Question 89 of 104
Melting points of group II-A elements are higher than those of group I-A because:
A
Atoms of II-A elements have smaller size
B
II-A elements are more reactive
C
Atoms of II-A elements provide two binding electrons
D
I-A elements have smaller atomic radius
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Atoms of II-A elements provide two binding electrons
Concept:

The melting point of a metal depends heavily on the strength of its metallic bond, which is dictated by the number of delocalized valence electrons it contributes to the "sea of electrons."

Solution:

  • Group I-A (Alkali metals) have an \( ns^1 \) configuration, meaning each atom provides only one valence electron for metallic bonding.
  • Group II-A (Alkaline earth metals) have an \( ns^2 \) configuration, meaning each atom provides two valence electrons.
  • This higher number of binding electrons in Group II-A creates a much stronger metallic bond, pulling the positive metal cores closer and requiring much higher thermal energy to break.


Why other options are incorrect:

  • While Group II-A elements are indeed smaller in size than Group I-A (Option A), the primary and most significant factor for the large difference in melting point is the doubling of the binding electrons.

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