Dot Structure of chromium trioxide CrO3 - #49

A simple procedure for writing 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 chromium trioxide. Chromium is an essential nutrient required for normal sugar and fat metabolism and works primarily by potentiating the action of insulin. It is included in several dietary supplements and vitamins. The chemical formula is CrO₃ .

Step 1: Connect the atoms with single bonds. 

Fig. 1: The CrO₃atoms connected with single bonds

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

Where n in this case is 4. Where V = (6 + 6 + 6 + 6 ) = 24 , V is the number of valence electrons of the molecule.

Therefore, P = 6n + 2 – V = 6 * 4 + 2 – 24  = 2   \  So, there is one double bond in the molecule.

Step 3 & 4: The  resonance structures of CrO₃ are as follows:

Fig. 2:  Lewis electron dot structures of CrO₃