•Chapter 8 •Homework posted•Lab Notes•Today’s Topic:

Bond Properties (Sec. 8.4- there is no 8.3!)

Electron Distribution in Molecules (8.5)

November 16, 2009

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)

Did you try this at home? Here’s the answer…

__# electrons__C = 4

H = 2 x 1 = 2Cl = 2 x 7 = 14

Total = 20

Organic Structures

CHCCHCH2

What can we do with Lewis Structures?

Bond Properties

1. Polarity

2. Bond Order

3. Bond Length

4. Bond Energy

Bond Types

Nonpolar Covalent

Polar Covalent

Ionic

Imagine theyare nuclei

Imagine this isa valence electron

Polarity

Electronegativity- The ability of an atom involved in a bond to attract electrons to itself Orbital energy, effective nuclear charge

Polarity

Electrons drawn closer to the more electronegative atom

Trend in Electronegativities

Bond Character: From Covalent to Ionic

In a C-O bond, which element will have a greater concentration of electron density?

1 2 3

15%5%

80%1. Carbon2. Oxygen3. Neither, they

will share the electrons equally

Bond Order

The number of bonding electron pairs between two atoms

Bond Length

Atom size

Bond order

Which bond is the longest?

1 2 3 4 5

12%

19%

45%

16%

8%

1. H - H2. H - Cl3. Cl - Cl4. Cl - Br5. Br - Br

Which bond is the shortest?

1 2 3 4

20%

36%40%

3%

1. N-N2. N=N3. NN4. All are the same

length