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