Transcript Slide 1

By: Megan Aldridge
-VSEPR stands for Valence Shell Electron Pair Repulsion
-Developed in 1957 by Canadian chemist, Ronald Gillespie
-Theory predicts the 3D shapes of individual molecules
-Based on the idea that the geometry of a molecule is determined
primarily by repulsion among the pairs of electrons associated with th
central atom. The pairs ca n be bonded or un-bonded (lone pairs)
-Only valence electrons of the central atom influence the molecular
shape
LONE PAIR
BONDED PAIR
1) Pairs of electrons in the valence
shell of a central atom repel each
other.
2) These pairs of electrons tend to
occupy positions in space that
minimize repulsions and maximize
the distance of separation between
them.
-There are three kinds of repulsions between valence
electrons of a molecule
-LP LP repulsions are stronger than LP BP repulsions which
are stronger than BP BP repulsions
LONE PAIR – LONE PAIR (LP, LP)
LONE PAIR – BONDED PAIR (LP, BP)
BONDED PAIR – BONDED PAIR (BP, BP)
Example#2
#1
Example
SHAPE – Bent
SHAPE – Tetrahedral
-The two lone pairs have
a stronger
repulsion tha
ANGLE
– 109.5º
the bonded pairs
so the
the 3D
Hs
- (hydrogen)
Used to show
and pushed
shape
of CH4downwards
* Shapes of Covalent Molecules with NO Lone Pairs of
Electrons Around the Central Atom*
Bond Angle - 180º
# OF Electron Pairs – 3
Examples – BeCl2, CO2, HgCl2
Bond Angle - 120º
# of Electron Pairs – 3
Examples – BCl3, BF3, SO3
Bond Angle – 109.5º
# of Electron Pairs – 4
Examples – CH4, ClO4, PO4, SO4
Bond Angle – 90º + 120º
# of Electron Pairs – 5
Examples – PCl5
Bond Angle - 90º
# of Electron Pairs – 6
Examples – SF6