Shapes of Molecules

Question 1

what is the co-ordination number

Answer 1

the amount of bonding pairs bonded to the central atom

Question 2

outline the shape and bond angles for molecules with 2 bonding pairs

Answer 2

linear
180

Question 3

outline the shape and bond angles for a molecule with 3 bonding pairs

Answer 3

trigonal pyramidal
120

Question 4

outline the shape and bond angles for a molecule with 4 bonding pairs

Answer 4

tetrahedral
109.5

Question 5

outline the shape and bond angles for a molecule with 5 bonding pairs

Answer 5

trigonal bipyramid
90 and 120

Question 6

outline the shape and bond pairs for a molecule with 6 bonding pairs

Answer 6

octahedral
90

Question 7

whats the effect of lone pairs on the central atom in a molecule, on the bond angles

Answer 7

• makes bond angles smaller

Question 8

why do lone pairs make bond angles smaller

Answer 8

because lone pair-bond pair repulsion is stronger than bond pair- bond pair repulsion
- this means that theres a larger bond angle between lone-bond vs bond-bond

Question 9

what is each lone pair worth in terms of angle size

Answer 9

2.5

Question 10

outline the shape of a molecule with 3 bonding pairs and one lone pair

Answer 10

trigonal pyramidal
107

Question 11

how do you find the shape of a molecule

Answer 11

1. find number of electrons in the outer shell of the central atom
2. add one electron for each atom that the central atom is bonded to
3. add one for each number of negative charge and subtract one for each number of positive charge
4. divide the number by 2 to find the number of electron pairs
5. compare the number of pairs to number of bonds to find the number of lone pairs and bonding pairs