Molecular Geometry & Polarity

Molecular Geometry - VSEPR Model

1) All bonds from the central atom are called charge clouds.

a) always consider a multiple bond as a single charge cloud!!!

2) If there are any lone pairs of e^- on the central atom, they are also considered charge clouds.

Have to draw the correct Lewis dot structure to determine!!!

Ex:

CO₂

C₂H₄

H₂O

2 charge clouds

3 charge clouds

4 charge clouds

2 Charge Clouds

1) Charge clouds = 2 (2 bonded)

Ex: CO₂

A) Geometry = linear

2) Charge clouds = 2 (1 bonded, 1 lone)

Ex: CO

A) Geometry = linear

3 Charge Clouds

1) Charge clouds = 3 (3 bonded)

Ex: CO₃^-2

A) Geometry = trigonal planar

2) Charge clouds = 3 (2 bonded, 1 lone)

Ex: NOF

B) Geometry = bent/v-shaped

4 Charge Clouds

1) Charge clouds = 4 (4 bonded)

Ex: CH₄

A) Geometry = tetrahedral

2) Charge clouds = 4 (3 bonded, 1 lone)

Ex: NH₃

A) Geometry = trigonal pyramidal

4 Charge Clouds

3) Charge clouds = 4 (2 bonded, 2 lone)

Ex: H₂O

A) Geometry = bent/v-shaped

Polar Molecule = an unequal sharing or distribution of electrons in a compound.

Polarity is caused by:

1) Difference in electronegativity between elements in a bond

2) Asymmetrical molecule shape

Shape = Tetrahedral

Symmetric = Nonpolar

Shape = Trigonal Pyramid

Asymmetric = Polar

Polar Molecule = an unequal sharing or distribution of electrons.

Polar Molecule = an unequal sharing or distribution of electrons in a compound.

Ex: Which of the following molecules would be polar? Why?

H₂O

HF

CO₂

C₂H₂

Shape = Bent

Shape = Linear

Shape = Linear

Shape = Linear

Asymmetric = Polar

Symmetric = Non-Polar

Asymmetric = Polar

Symmetric = Non-Polar