1 chapter 9 — dot structures — part 1 · 1 chapter 9 — dot structures — part 1 1 ......

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