NEETChemistryChemical Bonding and Molecular Structure
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The B ₂ molecule is paramagnetic in nature. Reason (R): The highest occupied molecular orbital in B ₂ is a 2 p _ z orbital containing two unpaired electrons. In the light of the above statements, choose the most appropriate answer from the options given below.
Options
- AAssertion (A) is true but Reason (R) is false.
- BBoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- CBoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
- DBoth Assertion (A) and Reason (R) are false.
Correct answer
A. Assertion (A) is true but Reason (R) is false.
Step-by-step solution
The total number of electrons in a B ₂ molecule is 10. For molecules with up to 14 electrons, the molecular orbital energy level sequence is: 1 s Filling the 10 electrons, the electronic configuration of B ₂ is: 1 s ^2, ^ * 1 s ^2, 2 s ^2, ^ * 2 s ^2, 2 p _ x ^1 = 2 p _ y ^1 Since there are two unpaired electrons in the degenerate 2 p _ x and 2 p _ y orbitals, B ₂ is paramagnetic. Thus, Assertion (A) is true. The highest occupied molecular orbitals are 2 p _ x and 2 p _ y , not 2 p _ z . Thus, Reason (R) is false.