Classification of Bonds

Two main groups: • Ionic (complete transfer of electrons) Metal + nonmetal

• Covalent (sharing of electrons) Nonmetal + Nonmetal

However, Covalent Bonds don’t always share equally!

Nonpolar covalent

Polar covalent

Covalent bonds- 2 types

Nonpolar Covalent bond • A covalent bond in which the bonding

electrons are shared equally by the two atoms.

• Resulting in no charge on the atoms

Polar Covalent Bond • Bonds between nonmetal compounds • Electrons unequally shared

• The more electronegative atom pulls the e- closer to it so it is more negative

• The atom that is less electronegative has its e- pulled away so it is more positive.

Example 1: Oxygen-Hydrogen • This shared pair of atoms has a large

difference in electronegativities. • Oxygen is more electronegative than

hydrogen. • This means the e- pair will spend their time

closer to the oxygen.

• This oxygen has more e- around it for most of the time, so it has a slight negative charge and the hydrogen has less e- so it has s slight positive charge.

• Over all neutral charge

Example 2 • HCl

– Is this bond ionic or covalent? • covalent

– Which atom is more electronegative? • Cl

– Which atom will pull e- towards itself? • Cl

– What is the partial charge of Cl? • δ-

– What is the partial charge of each H? • δ+

Example 3

• H2O

• Br2

• Polar

• Nonpolar

Now you practice

• Page 9-10 (#1-9) • Stop at the whole molecule

Polar Bond vs. Polar Molecule

Polar bond vs. molecule polar covalent bond: a bond that has opposite partial charges on each side because of unequal sharing of e-. polar molecule: a molecule that can be turned so that it has opposite partial charges on opposite sides.

Polar molecule Must have both: 1. At least one polar bond 2. An “axis of symmetry” – one partial positive side & one partial negative side. (cut in half)

Polar vs. nonpolar Molecules If the atoms attract electrons around the central atom symmetrically, the molecule is non-polar

B

F F

F

C O O

O

H H

If the atoms pull electrons around the central atom asymmetrically, the molecule is polar (cut in half)

Examples:

Now you practice