# VSEPR Theory Valence Shell Electron Pair Repulsion.

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VSEPR Theory Valence Shell Electron Pair Repulsion

So, what do we do with VSEPR? Assume that atoms will orient themselves in order to minimize electron pair repulsions Use that information to illustrate what molecules and ions look like

vs.

So, what do we need to know? the difference between a lone pair and a bonding pair that both lone pairs and bonding pairs are considered effective pairs of electrons that a multiple bond is one effective pair

So, how do we get started? Determine the Lewis dot structure. Count the number of effective pairs around the central atom and determine if any of those are lone pairs Match the number of effective pairs and lone pairs with the chart of shapes and bond angles that you’ve memorized!

The Magic VSEPR Chart 20Linear180° 30Trigonal planar120° 40Tetrahedral109.5° 41Pyramidal107° 42Bent104.5° 50Trigonal bipyramidal 90°,120°,180 ° 60Octahedral90°,180° Eff Lone Shape Bond Angle(s)

Linear CO 2 O=C=O

Linear There are 2 effective pairs around carbon. Thus, they want to be as far away from each other as possible.

Linear

Trigonal Planar BF 3 B F F F

Trigonal Planar There are 3 effective pairs around boron. Thus, they want to be as far away from each other as possible.

Trigonal Planar

Tetrahedral CH 4 H H C H H

Tetrahedral There are 4 effective pairs around Carbon, and none of them is lone. Thus, they want to be as far away from each other as possible.

Tetrahedral

Pyramidal NH 3 N H H H

Pyramidal There are 4 effective pairs around nitrogen, but 1 of them is a lone pair. Thus, the lone pair really wants to be away from the bonding pairs that want to be away from each other.

Pyramidal

Bent H2OH2O O H H

There are 4 effective pairs around oxygen, but 2 of them are lone pairs. Thus, the lone pairs really want to be away from the bonding pairs that want to be away from each other.

Bent

Trigonal Bipyramidal PCl 5 Cl P

Trigonal Bypyramidal There are 5 effective pairs around phosphorus, and none of them is a lone pair. Thus, the five pairs want to be as far away from each other as possible.

Trigonal Bipyramidal

Octahedral SCl 6 Cl S

Octahedral There are 6 effective pairs around sulfur, and none of them is a lone pair. Thus, the six pairs want to be as far away from each other as possible.

Octahedral

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