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Bond order

Bond order of CN⁻

Bond order 3, diamagnetic. 14 electrons: Nb = 10, Na = 4.

NC
  • C
  • N

CN⁻Cyanide ion

Bond order 3

14 electrons, all paired

  • Bond order3
  • Magnetismdiamagnetic
  • Electrons14

Molecular orbitals

14 electrons
3bond order
diamagnetic

(Nb − Na) / 2 = (10 − 4) / 2

1s1s2s2s2p2pσ1sσ*1sσ2sσ*2sπ2pσ2pzπ*2pσ*2pzC atomMoleculeN atomEnergy

The atom columns show neutral atoms; the ion has 1 more electron in the molecule.

σ1s² σ*1s² σ2s² σ*2s² (π2px² = π2py²) σ2pz²

Working

Bond order step by step

  1. CN⁻ has 14 electrons: 6 from C and 7 from N, plus one for the negative charge.
  2. With 14 electrons or fewer, the π2p pair lies below σ2pz and fills first.
  3. Configuration: σ1s² σ*1s² σ2s² σ*2s² (π2px² = π2py²) σ2pz²
  4. Bonding electrons Nb = 10, antibonding electrons Na = 4.
  5. Bond order = (Nb − Na) / 2 = (10 − 4) / 2 = 3.
  6. Every electron is paired, so CN⁻ is diamagnetic.

Class 11, Chapter 4 Chemical Bonding and Molecular Structure.

Questions

Bond order of CN-: quick answers

What is the bond order of CN-?

3. Bond order = (Nb − Na) / 2 = (10 − 4) / 2 = 3. Bonding electrons Nb = 10, antibonding electrons Na = 4.

Is CN- paramagnetic or diamagnetic?

Diamagnetic. Every electron is paired, so CN⁻ is diamagnetic.

What is the molecular orbital configuration of CN-?

σ1s² σ*1s² σ2s² σ*2s² (π2px² = π2py²) σ2pz², with 14 electrons in all.

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