The Working Method for Drawing Lewis Structures

The Working Method for drawing Lewis structures for molecules, anions and cations involves the following steps  

Characterise the species given as a neutral molecule, cation or anion and identify the central atom. 

Draw a ball and stick diagram for the polyatomic molecules, anions or cations, including localised double bonds. 

Determine the total number of valence shell electrons present, add electrons for a negatively charged anion, subtract electrons for a positively charged cation. 

Assign two electrons for all single bonds as xx (to identify the single bonded electron pairs). 

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