Kamis, 13 Desember 2012

Canonical Structures|Lewis Dot Structure of OCN- --- #45

A simple procedure for writing canonical Lewis Structures was given in a previous article entitled “Lewis Structures and the Octet Rule”.
Several worked examples relevant to this procedure were given in previous posts please see the Sitemap - Table of Contents (Lewis Electron Dot Structures).


Let us consider the case of  OCN- 


Step 1: Connect the atoms with single bonds. 

Connect the atoms of OCN- with single bonds

Fig. 1 : Connect the atoms of  OCN- with single bonds.

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


Where n in this case is 3. Where V = (6 + 4 + 5) – (-1) = 16 , V is the number of valence electrons of the molecule.
Therefore, P = 6n + 2 – V = 6 * 3 + 2 – 16  = 4    So, there are :  2 double bonds or a triple bond.

Step 3 & 4: The   resonance structures of  OCN-  are as follows:

Plausible Lewis dot structures of OCN-

Fig. 2 : Lewis resonance structures of  OCN-
 
Structures #1 and #3 are more stable due to less charge separation comparing to #2. Structure #3 is more plausible than #1 since the more electronegative O atom has the negative charge. Therefore stability decreases:   #3 > #1 > #2
The most plausible Lewis structure is #3 and the least plausible #2.


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