2.2.2 Shapes Of Simple Molecules + Ions

Question 1

What’s a valence shell electron

Answer 1

Outer electron

Question 2

How can pairs of electrons be shared

Answer 2

Covalent bond

Question 3

What are unshared pairs of electrons called

Answer 3

Lone pairs

Question 4

Why are electrons as far apart from each other as possible

Answer 4

They’re all negatively charged so will repel

Question 5

What electrons pairs repel the most

Why

Answer 5

Lone pairs

Closer to nucleus than bonding pairs

Question 6

What do we use to show the bond is pointing towards us

Answer 6

A wedge

Question 7

What do we use to show the bond is pointing away from us

Answer 7

A dashed line

Question 8

What does the shape of a covalent molecule depend on

Answer 8

The type + number of electron pairs that surround the central atom

Question 9

6 rules to help work out number of pairs

Answer 9

1. Find central atom in chemical formula
2. Work out number of outer shell electrons (group number)
3. Add to this number the number of atoms bonded to central atom
4. If it’s an ion, + ions take away charge and - ions add charge
5. Divide answer by 2 to find no. Of electron pairs
6. Can then work out number of bonding pairs/Lone pairs

Question 10

What’s the shape and bond angles of a molecule with 2 bonding pairs

E.g BeCl2

Answer 10

Shape - linear

Bond angles - 180*

Question 11

What’s the shape and bond angles of a molecule with 3 bonding pairs

E.g BF3

Answer 11

Shape - trigonal planar

Bond angles - 120*

Question 12

What’s the shape and bond angles of a molecule with 4 bonding pairs

E.g CH4

Answer 12

Shape - tetrahedral

Bond angles - 109.5*

Question 13

What’s the shape and bond angles of a molecule with 5 bonding pairs

E.g PCl5

Answer 13

Shape - trigonal bipyramidal

Bond angles - 120* + 90*

Question 14

What’s the shape and bond angles of a molecule with 6 bonding pairs

E.g SF6

Answer 14

Shape - octahedral

Bond angles - 90*

Question 15

For a negative ion, where has the extra electron come from

Answer 15

A metal

Question 16

For a positive ion, what has an electron been lost to

Answer 16

A non-metal

Question 17

What are the 4 radicals we need shapes + bond angles of

What are they

Answer 17

Carbonate - trigonal planar - 120*

Nitrate - trigonal planar - 120*

Sulfate - tetrahedral - 109.5*

Sulfur trioxide - trigonal planar - 109.5*

Question 18

What do some molecules have that will affect the shape of them

Answer 18

Lone pairs

Question 19

What is the greatest and least electron repulsion

Answer 19

Least Bonded pair + bonded pair
Bonded pair + lone pair
Most Lone pair + lone pair

Question 20

What’s a lone pair closer due to do it’s greatest repulsion

Answer 20

The nucleus

Question 21

What’s the shape and bond angles of a molecule with 3 bonding pairs and 1 lone pair

E.g

Answer 21

Shape - pyramidal
Bond Angles - 107*

E.g ammonia, NH3

Question 22

Why is a pyramidal molecule 107, slightly reduced from 109.5

Answer 22

Due to the lone pairs repelling more

Question 23

What’s the shape and bond angles of a molecule with 2 bonding pairs and 2 lone pairs

E.g

Answer 23

Shape - bent/ non-linear
Bond angles - 104.5*

E.g water, H20

Question 24

What geometry are both the molecules with lone pairs based on

Answer 24

Tetrahedral geometry

Question 25

What do all electrons do

Answer 25

Repel