Shapes Of Molecules

Question 1

What does the shape of a molecule depend on?

Answer 1

The shape of a molecule depends on the number of groups of electrons around the central atom

Question 2

A group of electrons can refer to what?

Answer 2

• a bonding pair
• 2 bonding pairs if double bond ect
• a lone pair

Question 3

What are the two main points of VSEPR theory?

Answer 3

a) groups of electrons repel each other
b) groups of electrons will arrange themselves around the central atom so that they are as far apart from each other as possible, to give a simple symmetrical arrangement

Question 4

a) what is the shape
b) and the angles
of an AB2 molecule
c) give an example
d) draw it

Answer 4

a) linear
b) 180
c) BeCl2

Question 5

a) what is the shape
b) and the angles
of an AB3 molecule
c) give an example
d) draw it

Answer 5

a) trigonal planer
b) 120
c) BF3

Question 6

a) what is the shape
b) and the angles
of an AB4 molecule
c) give an example
d) draw it

Answer 6

a) tetrahedral
b) 109.5
c) CH4

Question 7

a) what is the shape
b) and the angles
of an AB5 molecule
c) give an example
d) draw it

Answer 7

a) trigonal bipyramidal
b) 120 between equatorial, 90 between equatorial and axial
c) PCl5

Question 8

a) what is the shape
b) and the angles
of an AB6 molecule
c) give an example
d) draw it

Answer 8

a) Octahedral
b) 90
c) SF6

Question 9

If there is a tetrahedral distribution of electrons, two lone pairs and two bonding pairs, what is the molecules shape based on the atoms?
i) what would be the shape if there was only one lone pair?

Answer 9

Bent / V shaped

i) Pyramidal

Question 10

If there is a octrahedral distribution of electrons, but there are two lone pairs, what is the molecules shape based on the atoms?

Answer 10

Square planer

Question 11

If there is a trigonal bipyramidal distribution of electrons, but there is one lone pair, what is the molecules shape based on the atoms?

Answer 11

Distorted tetrahedral

Question 12

Do you consider lone pairs when you are considering groups of electrons? why?

Answer 12

Yes because lone pairs of electrons repel one another just like bonding pairs

Question 13

State the following in order of repulsion…

1) Lone pair –> bonding pair repulsion
2) Bonding pair –> bonding pair repulsion
3) Lone pair –> lone pair repulsion

Answer 13

3, 1, 2

Question 14

Why do lone pairs exert greater repulsion than bonding pairs?

Answer 14

Because they have more freedom to move