1.6 VSEPR Theory

What is a dipole

During a polar covalent sharing of electrons, the electron pair are pulled closer and shared unequally by the atom with higher EN.

That movement is known as a dipole and is a vector quantity

How to determine the polarity of an entire molecule

Combine all the vectors found within the molecule and place them head to tail to find the net dipole, which will indicate the polarity of the molecule

This addition of dipoles rely heavily on the shape of the molecule. This can be found using VSEPR theory

What does VSEPR stand for and what is the theory

V = Valence

S = Shell

E = Electron

P = Pair

R = Repulsion

This theory, developed by Canadian chemist Ronald Gillespie, is used to predict the molecular geometry within a molecule.

What are the 4 points of VSEPR theory

1. The central atom, (the atom with the largest binding capacity), plays the biggest role, and must be identified

2. Since electron clouds repel eachother, atoms organize themselves in such a way as to minimize the interactions between neighboring atoms, and avoid repulsion from peripheral electrons

3. Unbounded pairs of electrons occupy space and must be considered

4. VSEPR theory does not discriminate between single or multiple bonds, the respective angle remains the same

What are the seven common predicted VSEPR shapes

• Linear

• Angular

• Trigonal Planar

• Pyramidal

• Tetrahedral

• Trigonal Bipyramid

• Octohedral

What are the properties of a Linear molecular shape

Occurs when the central atom is bonded to two atoms and does not possess non-bound electrons

• the net dipole will be zero unless the two electrons arent identical

What are the properties of an angular molecular shape

Occurs when the central atom is bound to two atoms but does possess non-bound electrons.

• Net dipole will be in direction of the most EN atom

What are the properties of a trigonal planar molecular shape

Occurs when the central atom is bound to three atoms and does not possess non-bound electrons

• Net dipole will be zero unless the three electrons arent identical

What are the properties of a pyramidal molecular shape

Occurs when the central atom is bound to three atoms but does possess non-bound electrons

• Net dipole either toward peak or base depending on the most EN atom

• 3D shape represented using Wedge-dash diagrams, where the wedge represents an atom protruding out the paper, the dashes represent an atom fading into the paper, and the lines represent atoms in line with the surface (this is used for the next shapes as well)

What are the properties of a Tetrahedral molecular shape

Occurs when the central atom is bound to 4 atoms and does not possess non-bound electrons

• Net dipole will be zero unless the 4 electrons arent identical

What are the properties of a Trigonal Bipyramidmolecular shape

Occurs when the central atom is bound to 5 atoms and does not possess non-bound electrons

• Net dipole will be zero unless the 5 electrons arent identical

What are the properties of a octahedral molecular shape

Occurs when the central atom is bound to 6 atoms and does not possess non-bound electrons

• Net dipole will be zero unless the 6 electrons arent identical