Alkaline earth metals-Andreas Stasch

Question 1

True/false, the group 2 metals follows the trend of density increasing down the group.

Answer 1

Mainly true, but Be is the most dense! Strong metallic bonding.

Question 2

The period 2 elements usually are the ‘odd ones out’, true/false ?

Answer 2

True

Question 3

MgCl2–>? What type of reaction is this?

Answer 3

Mg+Cl2 Electrolysis

Question 4

4CaO + 2Al + (conditions) –> 3Ca + CaAl2O4

What are the conditions?

Answer 4

1200C and vacuum.

Question 5

Does Be favour more ionic or covalent character?

Answer 5

More covalent due to small size and high charge density, strong bonds are created.

Question 6

2M +O2 –>?
What metal is the exception and why?
How do these form in different metals?

Answer 6

2MO
Be, passivated by oxygen layer
Mg,Ca can burn in air
Sr,Ba can ignite in air if finely divided.

Question 7

2BaO + O2 + (conditions) –> 2BaO2

What are the conditions for this uptake?

Answer 7

500C uptake.

Question 8

M +2H2O(conditions) –> M(OH)2 + H2

Answer 8

Ca,Sr,Ba cold

Mg warm

Question 9

M+H2 –>MH2

Be does not react like this, what hydride does Be form and what is special about the structure?

Answer 9

BeH4, it has 3 centre-2 electron bonds

Be

Question 10

Be and Al are similar in properties. What relationship is this?

Answer 10

Diagonal relationship

Question 11

M+X2 –>MX2
M(OH)2/MCO3 +2HX –> MX2 +2/1H2O + (CO2)
What metal does not react as a carbonate/hydroxide?

Answer 11

Be

Question 12

Draw the structure of BeCl2 at low temperatures.

What happens at high temperatures?

Answer 12

Cl     
          /     \
Cl--Be       Be--Cl
         \      /
            Cl

BeCl2 becomes linear Cl–Be–Cl

Question 13

What crystalline structure does MO have?

Answer 13

rock salt

Question 14

What is the mp trend for MO?

Answer 14

MP decreases going down the group.

Question 15

Group 2 binds water ligands better than group 1, so what happens to the water exchange rate?

Answer 15

It decreases so complex has longer lifetime.

Question 16

M2+ cations in water are acidic, which one is the strongest and why?

Answer 16

Be as highest polarisation and stongest bonds.

Question 17

Define hard and soft ions.

Answer 17

Hard:small, high charge, inability to polarise, ionic bonding
Soft:large, low charge, easy to polarise, covalent

Question 18

RX+Mg–>MgRX

What is this called and what is its purpose?

Answer 18

Grignard reagent, is a good nucleophile and helps to add alkyl chains to carbonyl compounds.

Question 19

Mg2+ is useful in chloryphyll. Why?

Answer 19

Redox-inert character and strong ligand binding.