Group 2- Alkaline Earth

Question 1

What is the outer electron configuration?

Answer 1

ns2

Question 2

What type of elements are they?

Answer 2

Metallic solids

Question 3

Compare the boiling, melting point and enthalpy of atomisation with group 1

Answer 3

They are all higher than group 1
This is because they have stronger metallic bonding in their lattice
- they have 2 delocalised electrons rather than 1 per atom in lattice

Question 4

What is the chemistry based on?

Answer 4

The +2 oxidation state

Question 5

What stabilises ionic group 2 compounds?

Answer 5

Low 1st and 2nd I.E. And high lattice enthalpy of salts

It is favourable for them to be ionic compounds

Question 6

Why are group 2 metals less reactive than group 1 metals?

Answer 6

They have a coating of oxide on their surface

Question 7

Which element is an exception?

Answer 7

Beryllium

Question 8

Describe the trend in IE down the group

Answer 8

It decreases due to more shells and lower zeff (increased shielding)

This means electrons are easier to remove

Question 9

Describe the trend in atomic radius down the group

Answer 9

The radius increases due to more shells

Question 10

Which structure is BeCl2 similar to?

Answer 10

It is similar to Alcl2 apart from Be has dative colavent bonds to Cl due to high degree of covalent character

Question 11

Why is beryllium an exception?

Answer 11

Be2+ is small and so highly charge dense
This means it is strongly polarising and has a high degree of covalent character
It draws electrons towards itself

Question 12

Why is Be2+ acidic in solution?

Answer 12

Due to its polarising power

Question 13

Give examples where Be is an exception

Answer 13

It doesn’t react with water
Be compounds have greater covalent character
Beryllium is amphoteric
Be2+ is acidic whereas others are neutral

Question 14

Describe the trend of covalent character down the group

Answer 14

As the group descends, the atoms become more electronegative and so they decrease in covalent character

Question 15

What is the most common group 2 organometallic

Answer 15

Those that contain Mg
Mg has high charge density so they have a high degree of covalent character
Carbon is negatively polarised- nucleophiles

Question 16

How is a Grignard reagent formed?

Answer 16

RX + Mg -> RMgX

Question 17

Describe the reactivity of group 2 organometallics

Answer 17

They are very reactive

Question 18

What properties are unexpected of heavier G2 atoms?

Answer 18

They are more ionic that expected
They are kinetically unstable
They are thermodynamically unstable

Question 19

Show equations for dissolve KCl, lattice enthalpy and hydration

Answer 19

Solvation
kCl -> k+(aq) + Cl-(aq)

Lattice enthalpy
kcl -> k+(g) + Cl-(g)

Hydration
k+(g) + Cl-(g) -> k+(aq) + Cl-(aq)

Question 20

How can you calculate the enthalpy of solvation (when a solid dissolves and forms aqueous ions)

Answer 20

Solvation= lattice enthalpy - hydration of ions

Hydration of Ions= lattice enthalpy + solvation

Question 21

Describe the entropy changes when a crystal dissolves

Answer 21

1) breaking down ordered lattice (increase)

2) solvation of ions (decrease)- hydrogen bonds

Question 22

Describe how temperature plays a part in solubility

Answer 22

As temperature increases T^S increases
^G becomes more negative (more spontaneous)
The salt becomes more soluble

Question 23

What is the trend between coordination as you go down the group?

Answer 23

Coordination to Ligands is weaker down the group as charge density decreases