Bonding orbital, definition

It is clear from this definition that bond (orbital) conjugation is far more common than bond (electron) delocalization. Conjugation does not always lead to bond delocalization and, accordingly, it is not correct to use the two terms indiscriminately13. It is well known that polyenes are typical examples of double bond conjugation but, as has been demonstrated by Dewar and coworkers, their heats of formation as well as other properties can be reproduced by appropriate bond increments. Thus polyenes are not examples of bond or electron delocalization. 

Earlier in this chapter, you learned the definition of bond order in the valence bond theory. In molecular orbital theory, the bond order is defined as one-half the difference between the number of electrons in bonding orbitals and the number of electrons in antibonding orbitals. Mathematically, this can be expressed as... 

You will recall that one pair of electrons shared between two atoms constitutes a single chemical bond this is Tewis original definition of the covalent bond. In C2 there are two paris of electron in the pi bonding orbitals, so we have what dicarbon... 

From this definition, other indices are derived the bonding orbital information index ly... 

Conversely, using the definition of antibonding orbitals, the anti-bonding orbital for ethylene may be written as ... 

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