VSEPR theory

Valence Shell Electron Pair Repulsion.

Understanding the secrets behind how electrons are arranged in an atom and their impact on chemical properties.

​- Welcome to the lecture on VSEPR Theory!

- VSEPR stands for Valence Shell Electron Pair Repulsion theory.

- It is a fundamental concept in chemistry used to predict molecular geometry.

- Understanding VSEPR theory helps us visualize how atoms are arranged in a molecule.

Molecular Geometry

- Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule.

- It determines a molecule's shape, which in turn affects its chemical and physical properties.

VSEPR Theory - Basic Idea

- VSEPR theory is based on the idea that electron pairs (bonding and non-bonding) around a central atom will arrange themselves in a way to minimize repulsion.

- This leads to specific molecular geometries.

Electron Pair Repulsion

- Electrons repel each other due to their negative charges.

- Bonding pairs and lone pairs of electrons will arrange themselves to be as far apart as possible.

Electron Pair Arrangement

- Two types of electron pairs: bonding pairs (shared between atoms) and lone pairs (non-bonding pairs).

- The arrangement of these pairs determines molecular geometry.

VSEPR Geometries

- There are several basic VSEPR geometries:

  1. Linear

  2. Trigonal Planar

  3. Tetrahedral

  4. Trigonal Bipyramidal

  5. Octahedral

Linear Geometry (AX2)

 - Example: BeCl2
- Explanation of the arrangement of bonding and non-bonding pairs.

Trigonal Planar Geometry (AX3)

 - Example: BF3
- Explanation of the arrangement of bonding and non-bonding pairs.

Tetrahedral Geometry (AX4)

 - Example: CH4
- Explanation of the arrangement of bonding and non-bonding pairs.

Trigonal Bipyramidal Geometry (AX5)

 - Example: PCl5
- Explanation of the arrangement of bonding and non-bonding pairs.

Octahedral Geometry (AX6)

 - Example: SF6
- Explanation of the arrangement of bonding and non-bonding pairs.

Bent and Trigonal Pyramidal Geometry (AX6)

 - Example: H2O (bent) and NH3 (trigonal pyramidal)
- Explanation of the arrangement of bonding and non-bonding pairs.

Multiple Choice

 A lone pair is defined as

• A pair of bonding electrons
• One non-bonding electron
• A pair of non-bonding electrons
• A pair of electrons on the central atom

Multiple Choice

What is the VSEPR theory used to predict?

• Bond Strength
• Polarity
• Molecular Shape
• Electronegativity

Multiple Choice

Which of the following shapes has an unshared pairs of electrons on the central atom? 

• Bipyramidal
• Bent
• Trigonal Planar
• Tetrahedral

Multiple Choice

Which molecule would have this molecular geometry?

• BF₃
• CH₄
• PCl₅
• CO₂

Multiple Choice

What molecule could this be? 

• BF₃
• CH₄
• H₂O
• CO₂

Multiple Choice

What molecule could this be? 

• H₂O
• CCl₄
• PCl₅
• NaCl

Multiple Choice

Who could this be? 

• CO₂
• NH₃
• H₂S
• CH₄

Multiple Choice

Who could this molecule be?

• CH₄
• CO₂
• PCl₅
• BF₃

Multiple Choice

Who could this be?

• H₂O
• NH₃
• CO₂
• CH₄

Multiple Choice

What molecular geometry would PH₃ have?

• Trigonal Pyramidal

• Trigonal Bipyramidal

• Bent

• Linear

Multiple Choice

Consider the molecule below.  Determine the molecular geometry at each of the 2 labeled carbons.

• C1 = tetrahedral, C2 = linear
• C1 = trigonal planar, C2 = bent
• C1 = bent, C2 = trigonal planar
• C1 = trigonal planar, C2 = tetrahedral

Multiple Choice

How many electrons are shared in a triple bond?

• 6
• 3
• 6 pairs
• 5

Multiple Choice

What shape would this have?

• Trigonal planar

• Pyramidal

• Tetrahedral

• Bent

Multiple Choice

Choose the correct shape for this molecule:

• linear
• Trigonal pyramidal
• Bent
• Tetrahedral