VALENCE SHELL ELECTRON PAIR REPULSION (VSEPR) THEORY

The basic ideas of the valence shell electron pair repulsion (VSEPR) theory are:
Each set of valence shell electrons on a central atom is significant. The sets of valence shell electrons on the central atom repel one another. They are arranged about the central atom so that repulsions among them are as small as possible.
1.	Each bonded atom is counted as one region of high electron density, whether the bonding is single, double, or triple.
2.	Each unshared pair of valence electrons on the central atom is counted as one region of high electron density.

Molecule	Lewis Structure	Shape	Shape Name and Bond Angle	General Formula	
CO2	

		Linear
180o	AX2	
BF3	

		Triginal Planar
120o	AX3	
CH4	

		Tetrahedral
109.5o	AX4	
PCl5	

	

	Triginal bipyramidal
(90o, 120o)	AX5	
SF6	

	

	Octahedral
(90o)	AX6	
H2O	

		Bent/Angular
104.5o	AX2E2	

NH3	

		Triginal Pyramidal
(107o)	AX3E2	

SF4

	

	Seesaw shape	AX4E	

VSERP Theory Understanding Concepts

1.	Explain how the words that the VSEPR acronym represents communicate the main ideas of this theory.

2.	Use VSEPR theory to predict the geometry of a molecule of each of the following substances. Draw a diagram showing the shape of each molecule.
qqqqqqqqqqqqqq.	
a.	BeI2 (s) 
b.	PF 3 (g) 
c.	H2S (g) 
d.	BBr3 (g)
e.	SiBr4 (l)
f.	HCl (g)

3.	Use VSEPR theory to determine the shape of each of the following polyatomic ions:
qqqqqqqqqqqqqq.	
a.	PO 43- 
b.	IO3-  
c.	IO4- 
d.	SO32-
e.	ClO2- 

4.	Use Lewis structures and VSEPR theory to predict the shapes of the following molecules:
a.	CO2 (g), carbon dioxide (dry ice)
b.	HCN (g), hydrogen cyanide (odour of bitter almonds)
c.	C 3H6 (g), propene (monomer for polypropylene)
d.	C 3H4 (g), propyne
e.	H 2CO (g), methanal (formaldehyde)
f.	CO (g), carbon monoxide (deadly gas)

5.	Use Lewis structures and VSEPR theory to predict the molecular shape of the following molecules. Include a 3-D representation of each molecule.
qqqqqqqqqqqqqq.	
a.	H2S (g), hydrogen sulfide 
b.	BBr3 (l), boron tribromide 
c.	PCl3 (l), phosphorus trichloride
d.	SiBr4 (l), silicon tetrabromide
e.	BeI2 (s), beryllium iodide
f.	CS2 (l), carbon disulfide
g.	HCOOH (g), acetic acid
h.	N2H4 (l), hydrazine
i.	H2O2 (l), hydrogen peroxide
j.	CH3CCCH3 (l), 2-butyne