Using the molecular orbital model, write electron configurations for the following diatomic species and calculate the bond orders. Which ones are paramagnetic? Place the species in order of increasing bond length and bond energy.
a. CN +
b. CN
c. CN -

A) The bond order of the diatomic species ;

B) The paramagnetic specie is :  CN⁺

C) Arrangement following Increasing Bond energy : CN --- > CN⁺ --- > CN⁻

D) Increasing Bond Length : CN⁻ --> CN⁺ ---> CN

The Bond length of a diatomic specie is the inversely proportional to the bond energy. therefore the longer the bond length the weaker the bond energy and the shorter the bond length the stronger the bond energy. the molecular orbital used to write the electron configuration is as attached below.

Hence we can conclude that the Diatomic specie with the shortest bond length will have the strongest/highest bond energy and the paramagnetic specie is CN⁺.

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Bond orders

CN- =3

CN+ =2.5

CN =2

CN+ is paramagnetic

The order of increasing bond energy is CN <CN+ <CN-

The order of increasing bond length is CN- <CN+ <CN

Explanation:

The molecular orbital diagram of CN- is shown in the image attached. From that image, it is easy to deduce the bond order of the other related species. Bond length is in the reverse order as bond energy because the shorter the bond, the greater the bond energy. The specie with the highest bond order has the highest bond energy.

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