Section 3: Bonding - Shapes of Molecules

Question 1

A molecule with 4 bonding pairs has which shape and which bond angles?

Answer 1

tetrahedral

109.5

Question 2

A molecule with 3 bonding pairs has which shape and which bond angles?

Answer 2

trigonal planar

120

Question 3

A molecule with 2 bonding pairs has which shape and which bond angles?

Answer 3

linear molecule

180

Question 4

A molecule with 5 bonding pairs has which shape and which bond angles?

Answer 4

trigonal bi-pyramidal
90
120

Question 5

A molecule with 6 bonding pairs has which shape and which bond angles?

Answer 5

octahedral

90

Question 6

How do you work out if there are any lone pairs?

Answer 6

First you find out how many electrons are in the outermost shell of central atom , you then add to this number 1 electron for every covalently bonding atom.

To this total you subtract or add any number of electrons that need to be altered on account of the molecule being an ion.

This number is then divided by two. If the answer is greater than the number of bonding atoms then molecule must have lone pairs.

Question 7

Due to electron repulsion by how many degrees does a lone pair reduce the bond angle between a bonding pair ?

Answer 7

Approximately 2.5 degrees