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Question 840012
JEE Chemistry · Medium

Periodic Table and Periodicity: Mixed MCQ

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MixedMediumQuestion 840012

Question

Anomalous behaviour of the first element of a group is due to:
  1. A
    Small size, high charge density, no d-orbitals available for bonding
    Correct
  2. B
    High atomic mass
  3. C
    Extra protons
  4. D
    Larger radius than 2nd member

Correct answer

Small size, high charge density, no d-orbitals available for bonding

Explanation

First members of groups (Li, Be, B, C, N, O, F) show anomalous behaviour due to: (1) exceptionally small atomic/ionic size, (2) high charge density (polarising power), (3) maximum covalency = 4 (no d-orbitals in n=2 shell). Example: BeF₂ vs MgF₂, BF₃ vs BCl₃.

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