Lewis Dot Structure Method: Example diphosphene P2H2 - #28

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 and #27.

Let us consider the case of diphosphene P₂H₂

 Step 1: Connect the atoms with single bonds. 

Fig. 1: Connecting the atoms of P₂H₂  with single bonds

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

Where n in this case is 2 since P₂H₂ consists of 4 atoms but two of them are hydro gen.

Where V = (1 + 5 + 5 + 1 )  = 12  

Therefore, P = 6n + 2 – V = 6 *2 + 2 – 12 = 2    So there is one double bond and therefore the structure in Step 1  has one double bond.

Step 3 & 4: The Lewis structure of P₂H₂  is as follows:

Figure 2: Lewis structure for diphosphene, P₂H₄