How to Draw Lewis Structures 1. Count the total number of valence electrons (V e ) Hints: • Group number (A or B) = # of valence electrons for that atom • Add an electron for each negative charge • Subtract an electron for each positive charge • Don’t worry about which electron comes from which atom 2. Use single bonds to connect the atoms together in the proper arrangement. For a molecule to exist, there must be at least single bonds holding the atoms together in one unit. • If just one element has only one atom present, it is the central atom and all other atoms are bonded to it. • If two or more elements each has only one atom present, the central atom is usually the one furthest to the left and to the bottom of the periodic chart (least electronegative) • If there are two or more of the least electronegative atoms present, bind them together • Hydrogen is NEVER the central atom 3. If the central atom is from groups IVA-VIIA, do the following: • Calculate 8N x
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