is the number of chemical bonds
between a pair of atoms
. For example, in diatomic nitrogen
N=N the bond order is 3, in acetylene
H-C=C-H the bond order between the two carbon
atoms is also 3, and the C-H bond order is 1. Bond order gives an indication of the stability of a bond. The element with bond order value 0 cannot exist. Those with fractional values exist but are not stable.