1 chapter 9 — dot structures — part 1 · 1 chapter 9 — dot structures — part 1 1 ......
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1 Chapter 9 — Dot Structures — Part 1
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CHAPTER 9
Chemical Bonding I: Lewis Theory
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• Chemical bonds form because they lower the potential energy between the charged particles that compose atoms
• A chemical bond forms when the potential energy of the bonded atoms is less than the potential energy of the separate atoms
• To calculate this potential energy, you need to consider the following interactions: nucleus–to–nucleus
repulsions electron–to–electron
repulsions nucleus–to–electron
attractions
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H F
H F
C CH
H
H
H
N N
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O H+δ-δ
O F+δ -δ
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• During bonding, atoms may end with more or fewer electrons than the valence electrons they brought in order to fulfill octets
• This results in atoms having a formal charge FC = valence e− − nonbonding e− − ½ bonding e− • Sum of all the formal charges in a neutral molecule = 0 • In an ion, total equals the charge
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H N
H
C
O
N
H
H
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OO
O OO
O
€
1 + 22
= 32 = 1.5
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NH HH
HC
HO O Cl N
O
O
- + SO
O
O3 CH3CO2-, CO3
2-, SO42-
O O O OOO
Examples and bond orders will be worked out in class.
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BF3 SF4