# How can you use the VSEPR theory?

May 22, 2016

The bonding and structure of molecules, electron domain arrangement.

#### Explanation:

Note: answer may be lacking due to what I am required to know for my school course.

The valence shell electron repulsion theory relies on the basis that since electrons are negatively charged subatomic particles, the pairs of electrons will repel each other to be as far apart as possible in space. These pairs may be electron domains or bonds.

The VSEPR theory can also help with the deduction of bond angles between bonds on the same atom. If there are 2 pairs of electrons the linear shape would form, thus creating the bond angle ${180}^{\circ}$, example: carbon dioxide ($C {O}_{2}$).

If there are three bonds the molecular or electron domain geometry would be trigonal planar , with the bond angle being ${120}^{\circ}$, example: $B C {l}_{3}$.

If there are four bonds a tetrahedral shape would form, with the bond angle being ${109.5}^{\circ}$. example: $C {H}_{4}$

Other shapes for molecular geometry include:
1. linear $\to {180}^{\circ}$ (2 bonds, 3 electron domains);
2. bent $\to {104.5}^{\circ}$ (2 bonds, 2 electron domains);
3. bent $\to < {120}^{\circ}$ (2 bonds, 1 electron domain);
4. trigonal pyramidal $\to {107}^{\circ}$ (3 bonds, 1 electron domain);
5. trigonal bipyramidal $\to {90}^{\circ}$ and ${120}^{\circ}$(5 bonds)
6. octahedral $\to {90}^{\circ}$ (6 bonds);
7. see-saw $\to < {90}^{\circ}$ and $< {120}^{\circ}$ (4 bonds, 1 electron domain;
8. t shaped $\to < {90}^{\circ}$ (3 bonds, 2 electron domains);
9. square based pyramid $\to < {90}^{\circ}$ (5 bonds, 1 electron domain);
10. square planar $\to {90}^{\circ}$ (4 bonds, 2 electron domains).

The bond angles will vary depending on whether it is bonds that are present or non-bonded electron domains. In general the non-bonded electron domains will have a stronger repulsive force than the bonds.

Reference
Bylikin, Sergey, Gary Horner, Brian Murphy, and David Tarcy. Chemistry: Course Companion. Oxford: Oxford UP, 2014. Print.