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Question: Answered & Verified by Expert
Assertion : $\mathrm{B}_2$ molecule is diamagnetic.
Reason : The highest occupied molecular orbital is of $\sigma$ type.
ChemistryChemical Bonding and Molecular StructureAIIMSAIIMS 2005
Options:
  • A If both assertion and reason are true and reason is the correct explanation of assertion
  • B If both assertion and reason are true but reason is not the correct explanation of assertion
  • C If assertion is true but reason is false
  • D If both assertion and reason are false.
Solution:
2643 Upvotes Verified Answer
The correct answer is: If both assertion and reason are false.
In $\mathrm{B}_2$, total number of electrons $=10$
$$
\mathrm{B}_2 \rightarrow \sigma(1 s)^2 \sigma^*\left(1 s^2\right) \sigma(2 s)^2 \sigma^*(2 s)^2 \sigma\left(2 p_x\right)^1 \pi\left(2 p_y\right)^1
$$
Presence of unpaired electron shows the paramagnetic nature.
The highest occupied molecular orbital is of $\pi$-type.

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