chapter 8 second set of chapt. 8 homework dates extended until after break lab notes today’s...
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•Chapter 8 •Second set of Chapt. 8 homework dates extended until after break•Lab Notes•Today’s Topic:
Bond Properties (Sec. 8.4- there is no 8.3!)
Electron Distribution in Molecules (8.5)
November 16, 2009
What can we do with Lewis Structures?
Bond Properties
1. Polarity
2. Bond Order
3. Bond Length
4. Bond Energy
Bond Energy= The energy required to separate two bonded atoms
Remember-
It ALWAYS takes energy to break a bond!
Making bonds releases energy.
It ALWAYS requires energy to BREAK a bond!
The phosphate bond in ATP is not “broken”, it is hydrolyzed, a multi-faceted process that does result in a net release of energy. However, it involves more than the simple breaking of one bond.
Bond Energy in Ionic Compounds: Lattice Energy
Energy to separate all the ions
NaCl(s) Na+(g) + Cl-(g) H = Lattice E = -790 kJ/mol
Lattice Energy
Lattice energy = the energy it takes to pull ions in a solid apart
Remember Coulomb’s Law! Depends on ion SIZE Depends on ion CHARGE
Which has the strongest lattice energy?
1 2 3 4
38%
21%
12%
30%
1. MgCl2. BaCl3. KCl4. CsCl
Internal Properties of Molecules
ResonanceFormal ChargeOxidation NumberPartial Charge
Resonance Structures
A resonance structure is when more than one arrangement of electrons is possible (i.e., there is more than one reasonable Lewis structure)
Resonance and Bond Order
Bond order will not equal the # of bonds if there is more than one possible structure
What is the bond order of the C-O bond in the carbonate ion?
What is the bond order in SO2?
1 2. 3. 4. 5. 6.
6% 6%
16%
5%
49%
17%
1. 12. 1.253. 1.334. 1.55. 1.676. 2.0