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NEET 2023
Exam
NEET
Year
2023
Subject
Chemistry
Chapter
Chemical Bonding and Molecular Structure

NEET 2023 · Chemistry · Chemical Bonding and Molecular Structure

The correct order of energies of molecular orbitals of N _ 2...

The correct order of energies of molecular orbitals of N2{N}_{2} molecule, is:

Options

  1. A(σ1s)<(σ∗1s)<(σ2s)<(σ2s∗)<(π2px)=(π2py)<(π∗2px)=(π∗2py)<(σ2pz)<(σ∗2pz)( {\sigma}_{1s}) < ( {\sigma}^{*}1s) < ( {\sigma}_{2s}) < ( {\sigma}_{2s} * ) < ( {\pi}_{2{p}_{x}}) = ( {\pi}_{2{p}_{y}}) < ( {\pi}^{*}2{p}_{x}) = ( {\pi}^{*}2{p}_{y}) < ( {\sigma}_{2{p}_{z}}) < ( {\sigma}^{*}2{p}_{z} )
  2. B(σ1s)<(σ∗1s)<(σ2s)<(σ2s∗)<(π2px)=(π2py)<(σ2pz)<(π∗2px)=(π∗2py)<(σ∗2pz)( {\sigma}_{1s}) < ( {\sigma}^{*}1s) < ( {\sigma}_{2s}) < ( {\sigma}_{2s} * ) < ( {\pi}_{2{p}_{x}}) = ( {\pi}_{2{p}_{y}}) < \left({\sigma}_{2{p}_{z}}\right) < ( {\pi}^{*}2{p}_{x}) = ( {\pi}^{*}2{p}_{y} ) < ( {\sigma}^{*}2{p}_{z} )
  3. C(σ1s)<(σ∗1s)<(σ2s)<(σ2s∗)<(σ2pz)<(π2px)=(π2py)<(π∗2px)=(π∗2py)<(σ∗2pz)( {\sigma}_{1s}) < ( {\sigma}^{*}1s) < ( {\sigma}_{2s}) < ( {\sigma}_{2s} * ) < \left({\sigma}_{2{p}_{z}}\right) < ( {\pi}_{2{p}_{x}}) = ( {\pi}_{2{p}_{y}}) < ( {\pi}^{*}2{p}_{x}) = ( {\pi}^{*}2{p}_{y} ) < ( {\sigma}^{*}2{p}_{z} )
  4. D(σ1s)<(σ∗1s)<(σ2s)<(σ2s∗)<(σ2pz)<(σ∗2pz)<(π2px)=(π2py)<(π∗2px)=(π∗2py)( {\sigma}_{1s}) < ( {\sigma}^{*}1s) < ( {\sigma}_{2s}) < ( {\sigma}_{2s} * ) < \left({\sigma}_{2{p}_{z}}\right) < ( {\sigma}^{*}2{p}_{z} ) < ( {\pi}_{2{p}_{x}}) = ( {\pi}_{2{p}_{y}}) < ( {\pi}^{*}2{p}_{x}) = ( {\pi}^{*}2{p}_{y} )

Correct answer

B. (σ1s)<(σ∗1s)<(σ2s)<(σ2s∗)<(π2px)=(π2py)<(σ2pz)<(π∗2px)=(π∗2py)<(σ∗2pz)( {\sigma}_{1s}) < ( {\sigma}^{*}1s) < ( {\sigma}_{2s}) < ( {\sigma}_{2s} * ) < ( {\pi}_{2{p}_{x}}) = ( {\pi}_{2{p}_{y}}) < \left({\sigma}_{2{p}_{z}}\right) < ( {\pi}^{*}2{p}_{x}) = ( {\pi}^{*}2{p}_{y} ) < ( {\sigma}^{*}2{p}_{z} )

Step-by-step solution

The molecular orbitals filled with electrons according Afbaue, Pauli's exclusion and Hund's rules.

(σ1s)<(σ∗1s)<(σ2s)<(σ2s∗)<(π2px)=(π2py)<(σ2pz)<(π∗2px)=(π∗2py)<(σ∗2pz)( {\sigma}_{1s}) < ( {\sigma}^{*}1s) < ( {\sigma}_{2s}) < ( {\sigma}_{2s} * ) < ( {\pi}_{2{p}_{x}}) = ( {\pi}_{2{p}_{y}}) < \left({\sigma}_{2{p}_{z}}\right) < ( {\pi}^{*}2{p}_{x}) = ( {\pi}^{*}2{p}_{y} ) < ( {\sigma}^{*}2{p}_{z} )

The important characteristic feature of this order is that the energy of σ2pz{\sigma}_{2pz} molecular orbital is higher than that of π2pxandπ2py{\pi}_{2px}and{\pi}_{2py} molecular orbitals, it is due to 2s-2p mixing is allowed in case of nitrogen molecule.

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