VESPR theory Flashcards
What does VESPR stand for?
Valence Shell Electron Pair Repulsion
What is the VESPR theory used to do?
Predict the shape of polyatomic molecules
What does the theory assume?
That electron pairs within atoms will arrange themselves as far apart as possible in order to minimise repulsion.
What will the groups of atoms take up?
BASIC shapes according to the specific numbers of electron pairs (numbers of atoms attached)
For 2 electron pairs, what would the basic shape be?
Linear
For 3 electron pairs, what would the basic shape be?
Trigonal planar
For 4 electron pairs, what would the basic shape be?
Tetrahedral
For 5 electron pairs, what would the basic shape be?
Trigonal bipyramidal
For 6 electron pairs, what would the basic shape be?
Octahedral
What is the bond angle for a linear shape?
180
What is the bond angle for a trigonal planar shape?
120
What is the bond angle for a tetrahedral shape?
109.5
What are the bond angles for a trigonal bipyramidal shape?
90
120
What is the bond angle for a octahedral shape?
90
What equation is used to calculate the number of electron pairs?
No of outer electrons on central atom+ no of electrons donated by bonded atoms /2
What will the presence of non-bonding pairs do?
Distort the basic shape
Why does the presence of non-bonding distort the basic shape?
As the repulsion is greater between a non-bonding and a bonding pair
What will repulsion from non-bonding pairs do?
Reduced the bond angles to less than it would be in the basic shape
For a positive ion, what would you do to alter the question?
Subtract 1
For a negative ion, what would you do to alter the question?
Add 1
