Molecular orbital diagram of N₂
Bond order 3, diamagnetic. 14 electrons: Nb = 10, Na = 4.
Molecular orbitals
14 electrons3bond order
diamagnetic
diamagnetic
(Nb − Na) / 2 = (10 − 4) / 2
σ1s² σ*1s² σ2s² σ*2s² (π2px² = π2py²) σ2pz²
Why this shape
- Each N has 5 valence electrons. It uses three in one triple bond to N, so two are left as one lone pair.
- Steric number = one sigma bond + one lone pair = 2, so each N is sp hybridised. A double or triple bond counts once: only its sigma bond uses a hybrid orbital.
- Two electron pairs point in opposite directions, along a line (linear electron geometry). With only two atoms, the molecule itself is a straight line.
- Two atoms always lie on a straight line, so there is no bond angle.
- Both atoms are the same, so the bond is non-polar.
Lewis structure
10 valence electronsFormal charges: none
Filling the diagram
- N₂ has 14 electrons: 7 from each N.
- Up to N₂ (and its ions), the π2p pair lies below σ2pz and fills first.
- Configuration: σ1s² σ*1s² σ2s² σ*2s² (π2px² = π2py²) σ2pz²
- Bonding electrons Nb = 10, antibonding electrons Na = 4.
- Bond order = (Nb − Na) / 2 = (10 − 4) / 2 = 3.
- Every electron is paired, so N₂ is diamagnetic.
Class 11, Chapter 4 Chemical Bonding and Molecular Structure.
MO diagram of N2: quick answers
What is the molecular orbital configuration of N2?
σ1s² σ*1s² σ2s² σ*2s² (π2px² = π2py²) σ2pz². Up to N₂ (and its ions), the π2p pair lies below σ2pz and fills first.
What is the bond order of N2 from its MO diagram?
3: Nb = 10 and Na = 4, so (10 - 4) / 2 = 3. It is diamagnetic.
Why is σ2pz above π2p in N2?
Up to N2 the 2s and 2p orbitals are close in energy and mix, which pushes σ2pz above the π2p pair.