VSEPR

What is “vesper”? V alence S hell E lectron P air R epulsion theory According to VSEPR theory, the repulsion between electron pairs causes molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible. Able to use Lewis Structures to predict 3D geometry of molecule

V alence S hell E lectron P air R epulsion theory

According to VSEPR theory, the repulsion between electron pairs causes molecular shapes to adjust so that the valence-electron pairs stay as far apart as possible.

Able to use Lewis Structures to predict 3D geometry of molecule

Outline Hybridization 3D Geometry Balloons and a Table to Fill Out

Hybridization

3D Geometry

Balloons and a Table to Fill Out

Hybridization Step 1: Draw the Lewis Structure Step 2: Count the number of “things” stuck to the central atom. A “thing” can be another atom. A “thing” can be up to a lone-pair of electrons. A “thing” can NOT be a bond. Example: Thing 1 Thing 2 Thing 3 Thing 4

Step 1: Draw the Lewis Structure

Step 2: Count the number of “things” stuck to the central atom.

A “thing” can be another atom.

A “thing” can be up to a lone-pair of electrons.

A “thing” can NOT be a bond.

Example:

Hybridization Continued Step 3: Use flow chart to match “thing” number with hybridization.

Step 3: Use flow chart to match “thing” number with hybridization.

Hybridization -> Geometry Note that the hybridization for CH 4 is sp 3 S = 1 thing; p 3 = 3 more things; total = 4 things

Note that the hybridization for CH 4 is sp 3

S = 1 thing; p 3 = 3 more things; total = 4 things

Special Geometries The chart that we filled out was for regular geometries. Special geometries = lone pairs Lone pairs take up more space than the standard “thing” balloon. They squish atoms closer together. Example on next slide.

The chart that we filled out was for regular geometries.

Special geometries = lone pairs

Lone pairs take up more space than the standard “thing” balloon.

They squish atoms closer together.

Example on next slide.

Special Case Example H 2 O Thing 1 Thing 2 Thing 3 Thing 4 4 things = sp 3 hybridization Should look like: But actually looks like: Angle = < 109.5 degrees

H 2 O

4 things = sp 3 hybridization

Should look like:

But actually looks like:

Angle = < 109.5 degrees

Base Shapes