Topic 4

Question 1

1. Understand reasons for the trend in ionisation energy down Group 2

Answer 1

(Ionisation energies decrease)
Atomic radius - Increases down the group as more electron shells are added, moving electrons away from nucleus; Electron shielding - Increases down group as more inner electron shells reduce nuclear attraction
The atomic radius and shielding effects down groups are greater than the nuclear charge effect, leading to an overall decrease in ionisation energies as you move down group 2.

Question 2

2. Understand reasons for the trend in reactivity of the Group 2 elements down the
   group

Answer 2

Reactivity increases down group 2

Since it becomes easier to remove electrons further down the group, the reactivity of group 2 metals increases as you progress from beryllium (Be) down to radium (Ra).

The reactions of group 2 elements with water, oxygen, and chlorine become more vigorous as you descend the group.

Question 3

3. What are the reactions of the elements Mg to Ba in Group 2 with oxygen?

Answer 3

When a group 2 metal (M) burns in oxygen gas, a solid white oxide is formed:
2M(s) + O2(g) ➔ 2MO(s).

Question 4

3. What are the reactions of the elements Mg to Ba in Group 2 with chlorine?

Answer 4

Reaction of a group 2 metal with chlorine gas produces a solid white chloride:
M(s) + Cl2(g) ➔ MCl2(s)

Question 5

3. What are the reactions of the elements Mg to Ba in Group 2 with water?

Answer 5

Reaction of a group 2 metal (M) with cold water produces a metal hydroxide and hydrogen gas:
M(s) + H2O(l) ➔ M(OH)2(aq) + H2(g)

Question 6

4. What are the reactions of the oxides of Group 2 elements with water and dilute acid?

Answer 6

Group 2 metal oxides (MO) readily react with water to form metal hydroxides that dissolve in water:

MO(s) + H2O(l) ➔ M(OH)2(aq)

The pH of the resulting solutions increases down the group as the solubility of the hydroxides increases.

Question 7

4. What are the reactions of the Group 2 hydroxides with dilute acid?

Answer 7

Group 2 metal hydroxides (M(OH)2) also react with dilute acids such as hydrochloric acid (HCl) to form salt and water:

M(OH)2(s) + 2HCl(aq) ➔ MCl2(aq) + 2H2O(l)
The reactions become more vigorous down the group as the solubility of the compounds increases.

Question 8

5. What are the trends in solubility of the hydroxides and sulfates of Group 2 elements

Answer 8

Group 2 metal hydroxides become more soluble down the group
Group 2 metal sulfates become less soluble down the group.