Bond order

The bond order refers to the number of effective bonds in one molecule. It is defined as half the number that results from the difference between the bonding and antibonding valence electrons ( in the molecular orbitals ). In diatomic molecules can be determined as to whether a single, double or triple bond is present. Also can be explained why a He2 molecule is not stable, because when calculate the hypothetical molecule a formal bond order of zero is obtained.

Example

Bond order in O2 molecule:

Electron configuration of oxygen: 1s2, 2s2, 2p4

Involved in the binding are 2s2 and 2p4 molecular orbitals.

In binding, the 2s2 orbitals form from one bonding and antibonding MO (Sigma molecular orbital), which are staffed by two electrons.

The 2p4 orbitals form a bonding MO and MO 2 of each with 2 electrons.

The remaining two electrons, each occupied an antibonding orbital.

This gives a bond order of.