Group 2

Question 1

Melting point (general trend)

Answer 1

• Group 2 elements have high melting because:
• They have a giant metallic structure with strong attraction between positive metal ions & delocalised electrons .
• These metallic bonds take a lot of energy to break

Question 2

Density

Answer 2

• They are harder and have a higher density than group 1 elements because:
• Group 2 ions are smaller than group 1 ions so they can pack more closely together.

Question 3

Reactivity

Answer 3

Group 2 elements are all reactive metals with similar chemical reactions. This is because they all have 2 outer shell electrons.

Question 4

Atomic radius

Answer 4

Atomic radius increases down group 2.
Down the group there are more shells with more shielding, therefore the nuclear attraction to the outer electrons decreases.

Question 5

First ionisation energy (trend)

Answer 5

First I.E decreases down group 2.
Down the group the atomic radius increases as there are more shells with more shielding & a weaker nuclear attraction to the outer electron.

Question 6

Melting point (trend)

Answer 6

Melting pointing decreases down group 2.
As you go down a group, the ions get bigger so the attraction between positive metal ions & delocalised electrons decreases.

Question 7

Reaction of Mg with water

Answer 7

Cold water: very slow reaction, may see a few bubbles of H2 on the surface.
Mg(s)+ 2H2O(l) -> Mg(OH)2(s)+ H2 (g)
product- magnesieum hydroxide

Question 8

Mg with steam

Answer 8

Steam: white flame/light, white solid forms.
Mg(a)+ H2O(g) -> MgO(s)+ H2(g)
product- magnesium oxide

Question 9

Reaction of calcium with cold water

Answer 9

Effervescence (fizzing), white solid forms- some slightly soluble. Ca(OH)2 dissolves to give an alkaline solution.
Ca(s)+2H2O(l) -> Ca(OH)2(s or aq)+ H2(g)

Question 10

What observation is seen when barium reacts with cold water?

Answer 10

Effervescence, barium would disappear

Question 11

How is magnesium used to extract titanium from its ore?

Answer 11

The ore is reacted with carbon and chlorine
TiO2 + C + 2Cl2 -> TiCl4 + CO2
Then is reduced with magnesium
TiCl4 + 2Mg -> Ti + 2MgCl2

Question 12

What pH are group 2 hydroxides?

Answer 12

They are all bases

Question 13

What are the uses of magnesium hydroxide in medicine?

Answer 13

Indigestion tablets and ‘milk of magnesia’ which help to neutralise stomach acid

Question 14

What is the use of calcium hydroxide in agriculture?

Answer 14

Neutralises acidic soils

Question 15

What is the trend in solubility for group 2 sulfates?

Answer 15

The solubility decreases down the group

Question 16

testing for ions

How can the presence of Mg2+ ions be confirmed?

Answer 16

Done by adding aqueous sodium hydroxide to the solution. If Mg is present a thick white precipitate forms

Question 17

testing for ions

How can the presence of Ba2+ ions be confirmed?

Answer 17

Done by adding sulfuric acid or aqueous sodium sulfate to a solution. If barium is present a thick white precipitate forms

Question 18

What is the use of barium sulfate in medicine and why is it safe to use ?

Answer 18

Used in barium meal - BaSO4 can absorb x rays which allows soft tissue to be seen

It is insoluble so won’t be absorbed into the blood - barium ions are toxic

Question 19

Why does the boiling point increase down the group?

Answer 19

As you go down the group, the molecules are larger with a higher Mr and more electrons so have stronger van der Waals forces between molecules