1. Bellwork Tuesday
Draw the Lewis Structure and name the correct shaped molecule for all of the following.
BF3
CH4
HBr
NH3

2. 8.4 Polar Bonds and Molecules
In covalent bonds, the sharing of electrons can be equal
or it can be unequal.

3. Nonpolar Covalent Bonds
Nonpolar covalent bond - This is a covalent bond in which the electrons are shared equally.
EXAMPLES: H2
Br2 O2 N2
Cl2 I2 F2 Br Cl H N F I O O Br Cl H N F I

4. Polar Bonds and Molecules
If the sharing is unequal, the bond is referred to as a dipole.
A dipole has 2 separated, equal but opposite charges.
“∂” means partial _ +

5. Polar Bonds and Molecules
Polar covalent bond - a covalent bond that has a dipole
It usually occurs when 2 different elements form a covalent bond.
EXAMPLE:
H + Cl  H Cl

6. Polar Bonds and Molecules
Electronegativity - This is the measure of the attraction an atom has for a shared pair of electrons in a bond.
Electronegativity values increase across a period and up a group.

7. Electronegativity
Electronegativity values can be used to determine the degree of electron sharing which demonstrates the type of bond that will occur.
Difference > 2  Ionic
Difference  Polar
Covalent
Difference = 0 Nonpolar

8. The difference in electronegativity is:

9. Examples:
Identify the type of bond for each of the following compounds:
HBr
Br = 2.8
H = 2.1
0.7
.1 < < 1.9
Polar Covalent H Br

10. Examples: N N NaF F = 4.0 Na = 0.9 3.1 N2 N = 3.0 N = 3.0 0.0 Na F
> 2
Ionic
Non-Polar
Covalent N N

11. Molecular Polarity
If there is only one bond in the molecule, the bond type and polarity will be the same.
If the molecule consists of more than 2 atoms, you must consider the shape. To determine its polarity, consider the following:
Lone pairs on central atom
If so… it is polar
Spatial arrangement of atoms
Do bonds cancel each other out (symmetrical)?
If so… nonpolar
Do all bonds around the central element have the same difference of electronegativity?

12. Attractions Between Molecules
Van der Waals forces – the weakest of the intermolecular forces. These include London dispersion and dipole-dipole forces.
London dispersion forces – between nonpolar molecules and is caused by movement of electrons

13. Attractions Between Molecules
van der Waals forces(cont.)-
Dipole interactions – between polar molecules and is caused by a difference in electronegativity.

14. Attractions Between Molecules
Hydrogen bonds – attractive forces in which hydrogen, covalently bonded to a very electronegative atom (N, O, or F) is also weakly bonded to an unshared (lone) pair of electrons on another electronegative atom. O O H H H H O H H

15. Attractions Between Molecules
Ionic Bonding-occurs between metals and nonmetals when electron are transferred from one atom to another.
These bonds are very strong.

16. Summary of the Strengths of Attractive Forces
Ionic bonds hydrogen bonds dipole-dipole attractions LDF

17. Bellwork Wednesday
Write the correct attractive force: ionic bond, LDF, dipole-dipole, or hydrogen bond.
CO2
CF4
NH3
H2O
NaCl

18. Quick Review before Thursday Quiz
Name and write the formula for a compound containing sodium and nitrogen.
Draw Lewis Dot Structure then give the shape, polar/nonpolar, and the attractive force for each of the following:
BH3
PH3
CS2
CH4

19. Bellwork Friday
Draw the lewis diagram, name and write the formula for a compound containing calcium and phosphorous.
Draw Lewis Dot Structure then give the shape, polar/nonpolar, and the attractive force for each of the following:
SF6
SBr5-
XeCl2

20. Vocab Unit 11 page 56 Electronegativity Intermolecular Forces
Molecular Type
Bond Type
Valence
Non Polar Covalent
Polar Covalent
Crystal lattice
Metallic Bond