151Chap8PartII

# 151Chap8PartII - Lewis Structures Lewis structures are...

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11/4/2009 1 Lewis Structures Lewis structures are representations of molecules showing all electrons, bonding and nonbonding. Note: We only need to represent the VALENCE electrons. Writing Lewis Structures 1. Find the sum of valence electrons of all atoms in the polyatomic ion or PCl 3 molecule. – If it is an anion, add one electron for each negative charge. – If it is a cation, subtract one electron for each positive charge. 5 + 3(7) = 26 Writing Lewis Structures 2. The central atom is the least electronegative element that isn’t hydrogen. Connect the outer atoms to it by single bonds. Keep track of the electrons: 26 6 = 20 Writing Lewis Structures 3. Fill the octets of the outer atoms. Keep track of the electrons: 26 6 = 20 18 = 2 Writing Lewis Structures 4. Fill the octet of the central atom. Keep track of the electrons: 26 6 = 20 18 = 2 2 = 0

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11/4/2009 2 Writing Lewis Structures 5. If you run out of electrons before the central atom has an octet octet… …form multiple bonds until it does. Hints for Drawing Lewis Structures: In order to construct a Lewis structure you need to know how the atoms in a compound are connected to each other. Some general guidelines to follow are: The least electronegative atom, excluding hydrogen, is usually the central atom. Carbon has four bonds, nitrogen three, oxygen two and hydrogen and fluorine one. The number of bonds for halogens other than fluorine varies: one if the halogen is the more electronegative atom participating in if the halogen is the more electronegative atom participating in the bond, up to seven if it is the central atom. Sulfur has two bonds if it is the more electronegative atom, up to
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## This note was uploaded on 10/16/2011 for the course CHM 151 taught by Professor Yiguo during the Fall '09 term at Chandler-Gilbert Community College.

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151Chap8PartII - Lewis Structures Lewis structures are...

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