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•11:00 am-12:30 pm•EXAM #3 Results•Chapter 8

•Homework posted•Today’s Topic: Lewis Structures

November 11, 2009

Bond Types

1. Ionic Metal & Nonmetal

Charged atoms- based on electrostatic attraction

2. Covalent1. Nonmetal & nonmetal

2. Uncharged atoms- electrons are “shared”

3. e- - p+ attractions and p+- p+ or e- - e- repulsion between atoms

Metallic

Special type of covalent bonding for solids

Balance of Forces in Covalent Bonding

Bond will form when the balance of forces favors bonding (attractions > repulsions)

Valence Electrons

Lewis Structures (Lewis Dot Symbols) for Atoms

How many valence electrons does a Sn atom have?

1. 12. 23. 34. 45. 56. 67. 78. 8

Please make your selection...

1. Choice One2. Choice Two3. Choice Three4. Choice Four5. Choice Five6. Choice Six7. Choice Seven8. Choice Eight

Lewis Electron Dot Structures Describe Bonding in p-block Elements

What do those lines and dots mean?

A Lewis structure for a molecule describes the arrangement of electrons

Only valence electrons used Lines=bonds Dots= electrons that aren’t in a bond

What can a Lewis Structure do for us?

Rules for Drawing Lewis Structures

1. Write the skeletal structure2. Add up the total # of valence electrons3. Draw a bond between the central atom and each

surrounding atom4. Add lone pairs to the outer atoms to complete their

octets5. Add remaining electrons to central atom6. If central atom does not have an octet, “borrow”

electrons from other atoms (make double/triple bonds)- DO NOT ADD ELECTRONS (F and Cl do not form multiple bonds; C, N, O, P, and S do)

7. Sometimes you can’t complete an octet (B and Be)