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, #31 and #32.

Let us consider the case of acrylonitrile, C

_{3}H_{3}N:__Step 1__: Connect the atoms with single bonds.

Fig. 1: Connect the atoms of C _{3}H_{3}Nwith single bonds |

__Step 2__: Calculate the # of electrons in π bonds (multiple bonds) using

**formula (1)**:

Where n in this
case is 4 since C

_{3}H_{3}N consists of 7 atoms but 3 of them are H atoms.
Where V = 3*4 +
3*1 + 5 = 20

Therefore, P = 6n
+ 2 – V = 6 *4 + 2 – 20 = 6

**So, there are either i) 3 double bonds or ii) 1 triple and 1 double bond.**
The structure in
Figure 1 cannot have 3 adjacent double bonds because the middle carbon would
have 5 bonds.

The only
possibility is 1 triple and 1 double bond and the only possible arrangement is
shown in Steps 3 and 4:

__Step 3 & 4__: A draw of the Lewis structure of acrylonitrile

^{ }C

_{3}H

_{3}N is as follows:

Fig 2: Lewis dot structures of acrylonitrile. Structure #1 is the major contributor to the hybrid since there is an octet of electrons around each atom and there is no charge separation. |

Structure #1 is the major contributor to the hybrid - the most stable

**Lewis resonance structure**- since there is an octet of electrons around each atom and there is no charge separation.
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