1. Notes: 9.5 OBJECTIVES: Students will be able to (SWBAT)
Determine the polarity of molecules
QUESTIONS TO PONDER:
What is electronegativity?
How do you determine the bond character or type between 2 atoms?
What symbols are used to represent a dipole moment?
What does the polarity of a molecule depend on?
In order to determine the polarity of a molecule, what would be the first thing you should do?

2. Electronegativity and Polarity (Chapter 9, Section 5)

3. Electronegativity (EN) Difference
EN is a comparison of e- pulling strength
EN difference = difference of EN values of 2 atoms
Bigger EN value (chart on page 263)  stronger pull on electrons
Differences higher than 0 UNEQUAL SHARING OF ELECTRONS (more pull of e- to one side)
2.55
2.55
Difference = 2.55 – 2.55 = 0

4. Bond Character
Metal & nonmetal  IONIC  large difference (opposite sides of PT)
Nonmetal & nonmetal  COVALENT  small difference (close to each other on PT)
2 types of covalent bond
Non-polar covalent
EN difference is very small  equal sharing of e-
Polar covalent
EN differences is higher  unequal sharing of e-

5. Bond Types
EN DIFFERNCE

7. FULL POSITIVE CHARGE
FULL NEGATIVE CHARGE

8. Polar Covalent Bonds and Dipole Moments
“δ” – means “partial”
Arrow points
toward negative side
Cross is at the positive side
Arrow represents a DIPOLE MOMENT where one side is partially + and one side is partially -
2.6
4.0
4.0 – 2.6 = 1.4
Polar covalent

10. State whether IONIC, NONPOLAR COVALENT or POLAR COVALENT
Cl-Cl | 3.0 – 3.0 | = 0.0 nonpolar covalent
H-S | 2.1 – 2.5 | = 0.4 polar covalent
Na-Cl | 0.9 – 3.0 | = 2.1 ionic
O-H | 3.5 – 2.1 | = 1.4 polar covalent
I-Br | 2.5 – 2.8 | = 0.3 nonpolar covalent
Fe-O | 1.8 – 3.4 | = 1.6 polar covalent

11. Polarity of Molecules Polarity of an entire compound depends on:
Dipole moment of each bond
Shape and symmetry of the molecule
Location of lone pairs
Add/combine all dipole moments (arrows) for the TOTAL DIPOLE MOMENT of the molecule
Side with lone pairs have more partial negative charge

12. δ+ δ- δ+ δ-
Combined dipole moment:

17. Practice nonpolar N2 nonpolar HF polar CH4 nonpolar polar NH3 nonpolar
CH3F polar
nonpolar
polar
nonpolar
polar
polar