VSPER Molecular Geometry

NOTES

Let’s recap...

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VSPER Theory

Group Periodic Table

Molecular Shape 4-6
Example of Molecular Shape 7

Valence-Shell Electron-Pair
Repulsion (VSPER) Theory

VSPER: Electron repel each other , an electron pair
associated with particular atom will as far as apart from the
atom’s other electron pairs as possible.

A “group” of electrons is any number of electrons that
occupies a localized region around an atom. A single
bond, double bond, triple bond, lone pair, or single
electron all count as a single group.

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Group Periodic Table

Group 7, Group 6, Group 5, Group 4,
will have will have will have
7 valence 6 valence 5 valence will have
electrons. electrons. electrons.
So that it So that it So that it
need 1 need 2 need 3
electron electron electron
valence valence valence
to make to make to make
octet. octet. octet.

4 valence

electrons.

So that it

need 4

electron

valence

to make

octet.

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Group Periodic Table

Group 1, Group 2, Group 3, will have 3 valence
will have will have electrons. It will share
1 valence 2 valence electron to follow octet rule.
electron. electron.
So that it It will Second row element in
need 1 share periodic table (Li, Be, B, C, N,
electron electron O, F, Ne) are limited to total
valence to follow of eight electron(shared) in
to make octet
duplet. rule. their valence shells and
limited for four bond.
Hydrogen limited to two .

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Molecular Shape

The molecular shape is the three-
dimensional arrangement of nuclei joined
by the bonding groups. This is defined only

by the relative positions of the nuclei.

Molecular shape A = central atom
classified by : X = surrounding atom
E = nonbonding valence-electron group
m and n are integers

X X
A
Example : E

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Molecular Shape

Example




,
+




5

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Example Molecular Shape

sp Here is the
Example: BeCl2 example and the
Example: Example: molecular shape
Degree: 180° with the correct
Degree: 120° Degree: 109°
Name: Linear angle that we
Name: Trigonal planar Name: Tetrahedral will see in real.


Example:
Example:
Degree: 90°
Degree: 90°, 120°
Name: Octahedral
Name: Trigonal bipyramidal

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