Chapter 4 (group 2)

Question 1

Explain the trend in melting point in group 2

Answer 1

Decreases going down the group
Because:
-Ion cores have larger radius down the group
-So free electrons have less attraction to the nuclei
-So bonding is weaker and melting point goes down
-Magnesium is the exception

Question 2

What’s the trend in reactivity of group 2 elements

Answer 2

-Increases down the group
-ionisation energy needed to decrease down the group because increased shielding from extra shells
-reacts more readily down the group

Question 3

What’s the ionisation energy trend in the group 2 elements

Answer 3

-both first and second ionisation energies decrease down the group
-The second ionisation energy is higher than the first ionisation energy
E.g magnesium ionisation energy =737,1450,7732

Question 4

What do group 2 Elements form when reacting with water -use magnesium as an example

Answer 4

-Form a metal hydroxide and hydrogen as products
-Beryllium doesn’t react because if it lost electrons it would become too dense and wouldn’t react
-Mg + 2H2O = Mg(OH)2 + H2

Question 5

What happens when group 2 elements react with dilute acids -use calcium as an example

Answer 5

Forms a salt and a hydrogen

Ca + H2SO4 = CaSO4 +H2

The salts become less soluble going down the group

Question 6

What happens when group 2 oxides react with water-use strontium as an example

Answer 6

React steadily with water

Produces a metal hydroxide salt, which disassociates into metal ions and hydroxide ions, making it more alkaline

SrO + H2O =Sr(OH)2

Beryllium oxide doesn’t react with water and magnesium oxide reacts very slow

Question 7

What’s the solubility of group 2 Elements

Answer 7

Solubility increases going down the group- when group 2 oxides react with water, the products will be more alkaline going down the group

Down group = more soluble = more alkaline when oxide reacts with water

Question 8

What compounds of group 2 elements are bases

Answer 8

The group 2 oxides, carbonates and hydroxides are bases, so they’re alkaline and can neutralise acids

Question 9

What do both group 1 and 2 carbonates produce when they undergo thermal decomposition

Answer 9

Metal oxide + carbon dioxide

Question 10

What do group 1 and 2 nitrates produce when they undergo thermal decomposition

Answer 10

Metal oxide + nitrogen dioxide + oxygen

Question 11

What is the trend in thermal decomposition of group 1 and 2 carbonates and nitrates

Answer 11

They get more stable going down the group

So therefore More energy is needed is required for thermal decomposition as you go down each group

Question 12

What’s the trend and significant of charge density in group 2

Answer 12

further down the group, less density because more shells

both carbonates and nitrates have electrons delocalised across the ions

Question 13

what is the distorting effect in terms of polarity

Answer 13

the positive group 1 and 2 ions pull electrons towards them in the carbonates and nitrates

this polarises the carbonate and nitrate ions with the negative charge concentrated near the positive ions

the more polarised the carbonate/ nitrate is, the easier it will be for CO3^2- (carbonate) / NO3^2- (nitrate) to decompose to form CO2 /NO2

Question 14

how does polarity effect stability of group 1 and 2 carbonates/ nitrate

Answer 14

positive ikons with higher charge density will make the carbonate/ nitrate more polarised

going down group 1 and 2 the charge density gets lower

as charge density gets lower, the carbonates/ nitrates get less polarised- the less polarised the carbonate/ nitrate ion is the more energy needed to break of the CO2/NO2, therefore the more stable it is