Shapes of Molecules

Question 1

What is electron pair repulsion theory?

Answer 1

each pair around an atom will repel all other electron pairs
pairs of electrons adopt positions far apart to minimise repulsion

Question 2

What is the shape and bond angle of a molecule with two electron pairs?

Answer 2

linear and 180

Question 3

What is the shape and bond angle of a molecule with three electron pairs?

Answer 3

trigonal planar and 120

Question 4

What is the shape and bond angle of a molecule with four electron pairs?

Answer 4

tetrahedral and 109.5

Question 5

What is the shape and bond angle of a molecule with five electron pairs?

Answer 5

trigonal bipyramid and 120

Question 6

What is the shape and bond angle of a molecule with six electron pairs?

Answer 6

octahedral and 90

Question 7

How do we find the number of electron pairs in each molecule?

Answer 7

1. draw dot and cross diagram
2. look at group number to find how many electrons are needed for the central atom to have a full shell
3. count number of bonding and lone pairs

Question 8

What do lone pairs do?

Answer 8

affect shape of molecule

Question 9

How does lone pair repulsion affect the shape and bond angle of a NH3 molecule?

Answer 9

-ammonia has four electron pairs
-one lone pair and three bonding pairs
-bonding pairs attracted to nitrogen and hydrogen nucleus
-lone pair only attracted to nitrogen nucleus
-triangular pyramid and 107

Question 10

How does lone pair-lone pair repulsion affect the shape and bond angle of a H2O molecule?

Answer 10

-water has four electron pairs
-water has two bonding pairs and two lone pairs
-v shape and 104.5

Question 11

In Chlorine Tetrafluoride, how does lone pair-lone pair repulsion affect the shape an bond angle of the molecule?

Answer 11

-six electron pairs
-4 bonding pairs and two lone pairs
-lone pairs repel adopting furthest position
-square planar