Firstly draw lewis structure, then count the total number of bonds which is equal to $4$ here. Finally, count the number of bond groups between individual atoms, which is $3$. The bond order. The bond graph is composed of the "bonds" which link together "single port", "double-port" and "multi-port" elements see below for details. Each bond represents the instantaneous flow of. Since all of the resonance structures are equally dominant, we can see that all of these bonds consist of a $\sigma$ bond. We also see, that there is a $\pi$ bond in the first three structures. Each of them contributes equally, therefore it makes a third of a full contribution per bond, hence the bond order is expected to be about $1\frac13$. The bond order in sulfur dioxide, for example, is 1.5 the average of an S-O single bond in one Lewis structure and an S=O double bond in the other. In molecular orbital theory, we calculate bond orders by assuming that two electrons in a bonding molecular orbital contribute one net bond and that two electrons in an antibonding molecular orbital.