Simple Procedure for writing Lewis Structures – Example #1

Lewis Structures and the Octet Rule: A Simple Method to write Lewis Structures >  Simple Procedure for writing Lewis Structures – Example #1


A simple procedure for writing Lewis structures is given in a previous article entitled “Lewis Structures and the Octet Rule”.

Examples for writing Lewis structures following the above procedure are given bellow:

Consider the case of ozone O₃. Ozone is a very reactive gas, and even at low concentrations it is irritating and toxic. Event though it represents only a tiny fraction of the atmosphere is crucial for life on earth. Let us draw the Lewis Structures for ozone:

Step1: The central atom will be one of the oxygen atoms.  Connect the 3 atoms with a single bonds

O – O – O

             

Step 2: Calculate the # of electrons in π bonds (multiple bonds) using formula (1) in the article entitled “Lewis Structures and the Octet Rule”.

Where n in this case is 3 since O₃ consists of three atoms

Where V = (6 + 6 + 6 )  = 18  

Therefore, P = 6n + 2 – V = 6 * 3 + 2 – 18 = 2      So  there are 2 π electrons in O₃   and therefore 1 double   bond must be added to the structure of Step 1.

Step 3 & 4:  The 2 atoms are joined together with a double bond. Therefore the Lewis structure for O₃ is as follows:



Figure 1: Lewis structures for O_3. There are two equivalent resonance structures so in the molecule the bond between the O atoms is something between a double and a single bond. This fact has been proved experimentally