Bond Distance Depends on Occupation

In the neutral molecule H2, the interatomic distance is 0.74 A, considerably shorter than the bond in HJ (1.06 A). The smaller bond length in H2 is due to the fact that the bonding orbital (a -P b) is occupied by two electrons in H2 but only a single electron in H2L 

In the case of C J, finally, the electron is taken from the MO in the lowest spin singlet state. Since this is a bonding orbital, the bond length is larger than for the neutral molecule, or 1.30 A. There is a lower energy spin quartet ground state with a bond length of 1.40 A. In the latter case, there are only two electrons in the MO. 

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