chapter 8 homework posted lab notes today’s topic: bond properties (sec. 8.4- there is no 8.3!)...
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•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