13 - Molecular Shapes Worksheet With Answers printable pdf download

13 - Molecular Shapes Worksheet With Answers

Worksheet 13 - Molecular Shapes

The shapes of molecules can be predicted from their Lewis structures by using

the VSEPR (Valence Shell Electron Pair Repulsion) model, which states that

electron pairs around a central atoms will assume a geometry that keeps them as

far apart from each other as possible.

This is illustrated by the drawings below.

Six groups surrounding a central atom will form an octahedron.

All of the groups in this structure are at 90

or 180

to each other. All

positions are equivalent

Five groups will form a trigonal bipyramid. The two positions

pointing up and down are called the axial positions. They are at

180

to each other, and at 90

to the other three, equatorial

positions. The three equatorial positions are at 120

to each other.

There is more room in the equatorial positions, and large groups will

occupy these positions.

Four groups will form a tetrahedron. All of the angles in a

tetrahedron are 109.5

, and all positions are equivalent.

Three groups will form a flat triangle (trigonal planar).

Each of the angles is 120

and all positions are equivalent.

Two groups form a straight line (linear) with 180

between

them.

How does this apply to Chemistry?

The groups occupying these geometric positions will be either atoms bonded to

the central atom, or lone pair electrons on the central atom.

Lone pair electrons occupy more space than bonded electrons, so they will take

the equatorial position in the trigonal bipyramid.

Lone pair electrons will also occupy positions that put them as far apart from

each other as possible.

13 - Molecular Shapes Worksheet With Answers