Name	Lewis Structure	Kernel electrons	Valence electrons
Sodium	Na.	1s2 2s2 2p6	3s1
Phosphorus		1s2 2s2 2p6	3s2 3p3
Bromine		1s2 2s2 2p6 3s2 3p6 3d10 (≠ [Ar] = 1s2 2s2 2p6 3s2 3p6 )	4s24p5

Clark's Method (abbreviated) for determining bonding in covalent Lewis Structures:

• Add up all of the valence electrons in the structure (remember to add one electron for each negative charge, or subtract one for each positive charge)

  • If e^- = 6y + 2 where y = # atoms other than H, then octet rule is followed with single bonds only.

  • If e^- < 6y + 2 then probably have multiple bonding with the number of multiple bonds = /2 (remember a triple bond is 2 multiple bonds!).

  • If e^- > 6y + 2 then have an expanded valence shell.

  • If you can draw more than one structure, then chose the most symmetrical.

  • If two or more structures are equally symmetrical, then you probably have resonance and should show all structures connected by double arrows.

© R A Paselk

Last modified 27 March 2009