Rules for writing Lewis electron resonance structures– Formamidine- #37

A simple and automatic method for writing Lewis dot structures is 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  formamidine  (HNCHNH2).          

Step 1: Connect the atoms with single bonds. 

Fig.1: Connect the formamidine (HNCHNH2) atoms with single bonds

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

Where n in this case is 3 since formamidine has 3 non-hydrogen atoms.

Where V = 1*1 + 1*5 + 1*4 + 1*1 +1*5 +1*1 +1*1 = 18, V is the number of valence electrons of the atom.

Therefore, P = 6n + 2 – V = 6 *3 + 2 – 18 = 2   \  there is 1 double bond.

Step 3 & 4: The Lewis electron resonance structures of  formamidine  areas follows:

Fig. 2: Resonance Structures of formamidine

Structure #1 is the most stable electron dot structure because there is an octet of electrons around each atom and there is no charge separation.