After today, you will be able to… Define the term polarity Explain why certain atoms have more...

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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

Transcript of After today, you will be able to… Define the term polarity Explain why certain atoms have more...

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.