Simple Procedure for writing the Lewis Structures of CN+ - #31

A simple procedure for writing Lewis structures is given in a previous article entitled “Lewis Structures and the Octet Rule”. Relevant worked examples were given in the following articles: Examples #1, #2, #3 , #4, #5, #6,  #7,  #8, #9, #10, #11, #12, #13, #14,  #15, #16, #17, #18, #19, #20, #21, #22,  #23,  #24, #25, #26, #27, #28, #29, #30.

Let us consider the case of  the CN⁺cation:

Step 1: Connect the atoms with single bonds. 

Fig. 1: Connect the C and N atoms with a single bond

 Step 2: Calculate the # of electrons in π bonds (multiple bonds) using  formula (1): 
 

Where n in this case is 2 since  CN⁺ consists of 2 atoms.

Where V = (4 + 5 ) - charge  = 9 – 1 = 8  

Therefore, P = 6n + 2 – V = 6 *2 + 2 – 8 = 6   Therefore there are 6 πelectrons. So, there are 1) either 3 double bonds   2)  or 1 triple bond and an unshared electron pair.

Two atoms cannot be connected with 3 double bonds. However, it is possible that will be connected by a double bond. Two unshared electron pairs will be also added – so that in total 6 π electrons will be present :

Fig. 2: Lewis electron dot structures for the CN⁺ion. Structures 2 and 3 are minor contributors because of large charge separation. Structure 1 is a weak contributor too because the positive charge is on N which is more electronegative element than C.

 

Another possibility is that the two atoms will be connected by a triple bond. In this case an unshared electron pair will be added so that 6π electrons will be present. The Lewis structures of the CN⁺cation are as follows:

Fig. 3: Lewis electron dot structures for the CN⁺ion. Structure 4 is a major contributor because the positive charge is on the least electronegative atom (C atom). Structure 5 is a  minor contributor because of large charge separation.