Elements Of Life: Shapes of Molecules

Question 1

What is the shape of the molecules with

Total no. Areas = 2
Bond pair = 2
Lone pair = 0

Answer 1

Linear

Eg. BeCl 2

Question 2

What is the shape of the molecules with

Total no. Areas = 3
Bond pair = 3
Lone pair = 0

Answer 2

Trigonal planar

eg. BF3

Question 3

What is the shape of the molecules with

Total no. Areas = 4
Bond pair = 4
Lone pair = 0

Answer 3

Tetrahedral

Eg. CH4

Question 4

What is the shape of the molecules with

Total no. Areas = 4
Bond pair = 3
Lone pair = 1

Answer 4

Trigonal pyramid

Eg. NH3

Question 5

What is the shape of the molecules with

Total no. Areas = 4
Bond pair = 2
Lone pair = 2

Answer 5

Bent / V shaped

Eg. H2O

Question 6

What is the shape of the molecules with

Total no. Areas = 5
Bond pair = 5
Lone pair = 0

Answer 6

Trigonal bypyramid

Eg. PF 5

Question 7

What is the shape of the molecules with

Total no. Areas = 6
Bond pair = 6
Lone pair = 0

Answer 7

Octahedral

Eg. SF 6

Question 8

What is the bond angle of a linear shape molecule

Answer 8

180°

Question 9

What is the bond angle of a trigonal planar shape molecule

Answer 9

120°

Question 10

What is the bond angle of a tetrahedral shape molecule

Answer 10

109.5°

Question 11

What is the bond angle of a trigonal pyramid shape molecule

Answer 11

107°

Question 12

What is the bond angle of a bent / v shapes shape molecule

Answer 12

104.5°

Question 13

What is the bond angle of a trigonal bipyramid shape molecule

Answer 13

90° ( between 2 straight lines )

120° ( between dashes and wedge )

Question 14

What is the bond angle of a octahedral shape molecule

Answer 14

90°

Question 15

What is the electron repulsion theory (2)

Answer 15

1. Electron pairs will repel each other as far as possible
2. Shape of any molecule or ions is a consequence of the number of electron pairs which repel each other as far as possible

Question 16

What is another name for an electron pair

Answer 16

Area of electrons

Question 17

How do you work out the total no. of areas

Answer 17

No. of bond pairs + no. of lone pairs

Question 18

Definition of bond pair

Answer 18

2 shares electrons in a covalent bond

Question 19

Definition of love pairs

Answer 19

2 electrons in a pair not involved in bonding ( only counted it coming off the central atom )

Question 20

What is special about double and triple bonds

Answer 20

Meant to consider them as 1 bonding pair

Question 21

What does a lone pair do to a bonding angle and why

Answer 21

Reduce the bond angle by 2.5

• cos has a greater repulsion so pushes other atoms closer together

Question 22

Give an example of when a lone pair changes the bond angle

Answer 22

In sulphur dioxide ( SO2 )
= 2 bonding pair
= 1 lone pair

Total = 3 therefore = trigonal planar but the 120° angle becomes becomes 117.5

( because 120 - 2.5 )

Question 23

Give the electron repulsion theory for H2S

= 2 bonding pairs
= 2 lone pairs

Answer 23

Central S atom has 4 areas of electrons which repel as far as possible to give a bent shape