1. Chapter 6 -1 Bond Polarity (p. 198 – 201)
Covalent bonding = shared electrons
but, do they share equally?
Electrons are pulled, as in a tug-of-war, between the atoms nuclei
When the atoms in a bond are the same, the electrons are shared equally (as in diatomic molecules), and the bond that results is called a nonpolar covalent bond

2. Nonpolar Covalent Bond
e- are shared equally
symmetrical e- density
usually identical atoms

3. Electronegativity
The attraction of an atom for shared pair of electrons is called its electronegativity.
Fluorine has the greatest electronegativity.
The metals have low electronegativities.

4. Electronegativity Table (p. 198)
Increases up and to the right.

6. Bond Polarity
When two different atoms bond covalently, there is an unequal sharing of electrons
the more electronegative atom will have a stronger attraction for the shared electrons, and will acquire a slightly negative charge
called a polar covalent bond, or simply polar bond.

7. + - Polar Covalent Bond e- are shared unequally
asymmetrical e- density
results in partial charges
the positive and minus signs (with the lower case delta
) denote partial charges.
d+ d- + -

8. Electronegativity
Atom with higher e-neg  -
Atom lower e-neg  +

9. Figure 6-7, p.199 shows how the electronegativity difference can indicate the type of bond that tends to form

10. Bond Polarity Consider HCl H = electronegativity of 2.1
Cl = electronegativity of 3.0
the bond is polar
the chlorine acquires a partial negative charge, and the hydrogen a partial positive charge

11. Bond Polarity
Only partial charges, much less than a true 1+ or 1- as in ionic bond
Written as:
H Cl
d+ d-

12. Bond Polarity H Cl Can also be shown:
the arrow points to the more electronegative atom.
H Cl

13. Polar molecules
A polar bond in molecules composed of only 2 atoms makes the entire molecule “polar”
HCl has polar bonds, thus is a polar molecule.
a molecule in which one end has a partial positive charge and the other end has a partial negative charge is called a dipole

14. Learning Check Identify the type of bond between the following atoms
A. K-N
1) nonpolar ) polar 3) ionic
B. N-O
1) nonpolar 2) polar 3) ionic
C. Cl-Cl
1) nonpolar 2) polar 3) ionic

15. Polar molecules
The effect of polar bonds on the polarity of the entire molecule depends on the molecular shape
carbon dioxide has two polar bonds, but is linear:

16. Nonpolar Molecule
BF3 F B

17. Polar Molecule
H2O H O

18. Polar molecule
CHCl3 H Cl

19. Nonpolar
Polar
Ionic