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Chemical Bonding and Molecular Structure question

2019 · 9 Apr · Shift 2 · Q11
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  5. /2019 · 9 Apr · Shift 2 · Q11

Chemical Bonding and Molecular Structure question

2019 · 9 Apr · Shift 2 · Q11

JEE MainChemistryChemical Bonding and Molecular StructureMCQ+4 / −1
Among the following species, the diamagnetic molecule is
  1. A
    CO
  2. B
    B2B_2B2​
  3. C
    O2O_2O2​
  4. D
    NO
View written solutionFree

Correct answer: A

  1. Goal: Identify which species is diamagnetic.

A molecule is diamagnetic if all electrons are paired. If it has one or more unpaired electrons, it is paramagnetic.

  1. Check each option

(A) CO

  • Total electrons: 6+8=146 + 8 = 146+8=14
  • CO is isoelectronic with N2N_2N2​ and has all electrons paired in molecular orbitals.
  • Hence, CO is diamagnetic.

(B) B2B_2B2​

  • Total electrons: 5+5=105 + 5 = 105+5=10
  • MO configuration for B2B_2B2​: σ(1s)2 σ∗(1s)2 σ(2s)2 σ∗(2s)2 π(2px)1 π(2py)1\sigma(1s)^2\,\sigma^*(1s)^2\,\sigma(2s)^2\,\sigma^*(2s)^2\,\pi(2p_x)^1\,\pi(2p_y)^1σ(1s)2σ∗(1s)2σ(2s)2σ∗(2s)2π(2px​)1π(2py​)1
  • There are two unpaired electrons.
  • Hence, B2B_2B2​ is paramagnetic.

(C) O2O_2O2​

  • Total electrons: 8+8=168 + 8 = 168+8=16
  • MO configuration has two electrons in degenerate π∗(2p)\pi^*(2p)π∗(2p) orbitals unpaired.
  • Hence, O2O_2O2​ is paramagnetic.

(D) NO

  • Total electrons: 7+8=157 + 8 = 157+8=15
  • Odd number of electrons means at least one electron remains unpaired.
  • Hence, NO is paramagnetic.
  1. Conclusion

Only CO is diamagnetic.

Therefore, the correct option is: A\boxed{A}A​

  1. Comparison with stored correct answer
  • Derived answer: AAA
  • Stored correct answer: AAA

They match.

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