Molecular Geometry

Molecular Geometry

VESPR Theory

Molecular Geometry

• The specific three dimensional arrangement of atoms in molecules is referred to as molecular geometry.

• We also define molecular geometry as the positions of the atomic nuclei in a molecule. 

Remember...

• Elements that are bonded to another element, and therefore sharing electrons, are shown with one or more lines (either single, double or triple)

• Nonbonded electrons are shown by two dots and are called lone pairs because they are not in a bond

Multiple Choice

How are bonded elements shown in a Lewis Structure?

• With two or more dots

• Shown with one or more lines connecting the element to another element

• No lines or dots

• Bonded elements can not be drawn

Multiple Choice

Lone pairs are _______ __________ and are represented by ______ _________.

• Nonbonded electrons, two dots

• Bonded electrons, lines

• Protons, two dots

• Protons, lines

• The Lewis structure of carbon tetrachloride provides information about connectivities, provides information about valence orbitals, and provides information about bond character.

Multiple Choice

How many lone pair does each Chlorine atom have around it?

• 6

• 2

• 8

• 3

Tetrahedral

However, the Lewis structure provides no information about the shape of the molecule, which is defined by the bond angles. For carbon tetrachloride, each C-Cl bond angle is 109.5°. Hence, carbon tetrachloride is tetrahedral in structure:

Multiple Choice

Bond angles between carbon and chlorine in CCl₄ are

• 180⁰

• 90⁰

• 0

• 109.5⁰

Tetrahedral

Therefore, if the central atom has 4 things bonded to it and NO lone pairs (like CH₄)(or CCl₄) then the shape will be tetrahedral with bond angles of 109.5^⁰

Multiple Choice

Molecules that have 4 elements bonded to the central atom and have NO lone pairs are what shape?

• Triangle

• Tetrahedral

• Pyramidal

• Circular

Linear

If the central atom has two bonded pair (bonded with two other atoms) and no lone pairs that is called linear

Multiple Choice

A linear molecule has _______ bonded pairs and _______ lone pairs on the central atom.

• 2, 0

• 0, 2

• 2, 2

• 0, 0

Linear

Linear molecules have a bond angle of 180^⁰, meaning there is that much space between each set of electrons

Multiple Choice

The bond angle for a linear molecule is

• 180

• 360

• 90

• 109.5

Trigonal Planar

Trigonal Planar molecules have three bonded pair and no lone pair on the central atom

Trigonal Planar

An example of trigonal planar is boron trifluoride, BF₃. There are three things bonded to the central atom and the central atom has no lone pairs. The bond angle is 120⁰

Multiple Choice

What is the bond angle for trigonal planar?

• 180

• 120

• 90

• 109.5

Multiple Select

Which of the following are correct about molecules with a trigonal planar shape? Check all that apply

• 120^⁰

• No bonding pair

• Two bonding pair

• Two lone pair

• No lone pair

Bent

Molecules with two bonding pair and two lone pair are called bent. H₂O is the classic example of a bent molecule. There are two hydrogens connected to the central atom, oxygen, and the central atom has 2 lone pair.

Multiple Choice

What is the shape of a water molecule?

• Tetrahedral

• Linear

• Bent

• Trigonal Planar

Bent

The bond angle for a bent molecule is 104.5^⁰

Multiple Choice

What is the bond angle for a bent molecule?

• 120

• 180

• 90

• 104.5

Multiple Choice

A bent molecule has _______ lone pair and _______ bonded pair.

• 2, 2

• 0, 0

• 2, 0

• 0, 2

Multiple Choice

What shape is this?

• Bent

• Linear

• Tetrahedral

• Trigonal Planar

Multiple Choice

What molecular shape is this?

• Bent

• Linear

• Tetrahedral

• Trigonal Planar

Multiple Choice

What molecular shape is this?

• Bent

• Linear

• Tetrahedral

• Trigonal Planar