VSEPR Flashcards
VSEPR stands for
Valence shell electron pair repulsion
VSEPR predicts
Shape of molecules based on electron pair electrostatic repulsion
Why do molecules adapt their geometry
They pick the shape that allows valence electron pairs to be as far apart as possible bc electrons repel each other
Steric number equation
m + n from AxmEn
Steric number is the
Total number of positions occupied by atoms or lone pairs around the central atom
Order of strength of electron pair repulsion’s
lp-lp > lp-bp > bp-bp
Why are second and third bonds more repulsive
Because pi electrons increase electron density between bonded atoms beyond that of a sigma bond
Tend to occupy more space than single bonds
Multi bonds and lone pairs
Why do multi bonds and lone pairs occupy more space
Cause distortions and squeeze the rest of the molecule together
Most electronegative outer atoms have smallest bond angles because
Atom with big Electronegativity draws shared electrons in and away from the center, reducing repulsions
Lone pair effect relationship with Electronegativity of outer atoms
Increases together
Relationship between outer atom size and angle
Increase together
Cause of a most electronegative central atom
Larger bond angles
Tendency for less electronegative groups to occupy
Equal positions
Bond angle comparison between N(CF3)3 vs N(CH3)3
N(CF3)3 angles bigger than N(CH3)3 because Smaller outer group being less electronegative than larger group can cause opposite than expected effect so the more electronegative group causes smaller angles because electrons withdrawn more strongly.
