CHM 111 Molecular Geometry Pre-lab Questions

CHM 111 Molecular Geometry
Pre-lab Questions

1. Give a short summary of the main points of VSEPR theory.

- Valence Shell Electron Pair Repulsion (VSEPR) theory is used to predict the 3D shapes
of molecules.
- They show that electrons on a central atom push away from each other, within bonds or
lone pairs. They want to be as distant as possible.
- This pushing results in the atoms being certain shapes, such as tetrahedral, bent, or linear,
and allows us to find the bond angles.


2. Fill in the following blanks:
a) A molecule that has two atoms and two lone pairs of electrons off of the central atom
has a VSEPR formula of AX₂E2. Its approximate bond angle is 109.5°.

b) A molecule that has four atoms and one lone pair of electrons off of the central atom
has an electron pair geometry of trigonal bipyramidal. Its approximate bond angles are
<90°, <120°, and <180°.

c) A molecule that has four atoms and two lone pairs of electrons off of the central atom
has a octahedral electron pair geometry and a molecular shape of
square planar.

3. Draw Lewis Dot structures and predict the bond angles in the following molecules:

a) PF3 b) SF6
~ 109.5 ° 90° and 180°