After today, you will be able to…

•Define the term polarity•Explain why certain atoms have

more pull on electrons• Identify molecules as either polar or

non-polar based off of its symmetry• Identify which geometries will

generally be polar molecules

Unit 4: Chemical BondingPolar and Non-Polar Molecules

Day 4 - Notes

Day 4 - Notes

Polarity•Polar bond: Bonds where the

electrons are shared unequally between atoms–The atom that is more electronegative will pull the electrons closer to itself

–When atoms are different, each has a different pull on the electrons.

The shared electrons are held closer to fluorine, because it is

more electronegative.

H F

•Example: HF-δ+δ

Polar Molecule Example

•Non-polar bond: Electrons are shared equally between two atoms.–Atoms that are the same have the same pull on the shared electrons (same E.N. value)

•Example: H2

•Example: CCl4

HHBoth atoms have the same E.N.

value.

Non-Polar Molecule Examples

All atoms surrounding carbon are the same, therefore all electrons

are shared equally.

CClCl

Cl

Cl

General rules:

1.Different atoms around a central atom will always be polar molecules.

2.Same atoms around a central atom are always non-polar molecules.

How do you know if a molecule is polar or non-

polar?

Examples: Polar vs. Non-Polar

Non-polar

H2 versus HF

Polar

HH H F

Examples: Polar vs. Non-Polar

Non-polar

CO2 versus COS

Polar

OCO SCO

Examples: Polar Molecules

Polar

H2O NH3

Polar

OHH

NHH

H

Picture the unshared electrons as a different atom!

BENT and PYRAMID will always be polar.

Examples: Polar vs. Non-Polar

Non-Polar

CH4 CH3Cl

Polar

C HHH

H

CHH

H

Cl

Examples: Polar Molecule

Polar

CH2O

CO

H H

Although exceptions exist, for this class,

PLANAR will always be polar.