Register to reply

Molecular Orbital energy levels

by Duane
Tags: energy, levels, molecular, orbital
Share this thread:
Dec11-11, 07:01 AM
P: 8
Hi everyone
I'm currently studying the MO theory and ran into some trouble understanding orbital energy levels.

As I have previously read, σ bonds are stronger than ∏ bonds, therefore are lower in orbital energy. However, from the MO theory, the σ2p orbital is actually higher in energy than the ∏2p orbital in molecules like B2 and N2. But in molecules like O2 and F2, this sequence is reversed, with the ∏2p orbital having the higher orbital energy.

Can anyone tell me why?
Phys.Org News Partner Physics news on
An interesting glimpse into how future state-of-the-art electronics might work
How computing is transforming materials science research
Scientists describe a hybrid laminate material with magnetic and photoactive properties
Dec12-11, 05:56 AM
Sci Advisor
P: 3,593
a) I think you are referring to the anti-bonding orbitals, not the bonding ones.
b) the sigma bonds are not formed from pure p orbitals but from a superposition of 2s and 2p orbitals. The energetic distance of the 2s and 2p orbitals increases from left to right in a period, which explains the interchange of the energetic ordering of the molecular orbitals.

Register to reply

Related Discussions
Orbital Blocks and Energy Levels Biology, Chemistry & Other Homework 1
Molecular rotational levels Atomic, Solid State, Comp. Physics 0
Quantum Energy levels in atomic, molecular, nuclear and solid state physics Advanced Physics Homework 2
Molecular orbital and molecular wavefunction Advanced Physics Homework 0
Molecular Orbital Biology, Chemistry & Other Homework 2