Group 2,the alkaline earth metals

Question 1

What are group 2 elements called

Answer 1

The alkaline earth metals

Question 2

Why are group two elements called the alkaline earth metals

Answer 2

Their oxides and hydroxides are alkaline

Question 3

Which block of the periodic table do group two elements belong to

Answer 3

S block

Question 4

Which element do we not consider when describing the properties and trends of group two elements

Answer 4

Beryllium- it is no typical of the group

Question 5

Describe the electron arrangement of group 2 elements

Answer 5

• The elements all have an outer electron in and s-orbital.
• This s-orbital becomes further away from the nucleus going down the group

Question 6

Describe how the size of the atoms changes as you go down group 2

Answer 6

• The atoms get bigger as you go down the group.
• The atomic (metallic) radii increase because each atom has an extra main level of electrons compared with the one above it.

Question 7

Describe the trend in melting points as you go down group 2

Answer 7

• group 2 elements all have a giant metallic structure and so have high melting points
• going down the group, the electrons in the ‘sea’ of delocalised electrons are further away from the positively charged nuclei.
• As a result, the strength of the metallic bonds decreases going down the group.
• so the melting points of group 2 elements decrease slightly as you go down the group.

Question 8

What is the exception to the trend that the melting points of group 2 elements decrease slightly as you go down the group.

Answer 8

Magnesium.
Magnesium has the lowest melting point, so does not fit the trend. However, there is no simple explanation for this anomaly.

Question 9

What is the trend in reactivity going down group 2

Answer 9

The metals get more reactive as you go down the group

Question 10

What is the trend in first and second ionisation energies as you go down group 2

Answer 10

• Both the first and second ionisation energies decrease as you go down the group.
• it takes less energy to remove the electrons as they become further and further away from the positive nucleus.
• The nucleus is shielded by more inner electrons.

Question 11

How much energy is needed for the complete ionisation of group 2 elements

Answer 11

• An amount of energy equal to the sum of the first and second ionisation energies.
• this is because, in all of their reactions, group two elements lose their outer two electrons to form 2+ ions.

Question 12

What is oxidation

Answer 12

Loss of electrons

Question 13

What is reduction

Answer 13

Gain of electrons

Question 14

What type of reactions do group 2 elements always undergo

Answer 14

• REDOX reactions where group two elements are oxidised.
• The group two metals go from oxidation state 0 to oxidation state +2

Question 15

What is the equation for the reaction of a group 2 metal with water, where M is any group two metal

Answer 15

M (s) + 2H20 (l) —> M(OH)2 (aq) + H2 (g)

Question 16

Describe the trend in the hydroxides of group 2 elements as you go down the group

Answer 16

• They become more soluble as you go down the group:
  1) magnesium hydroxide is almost insoluble, it is held as a suspension in water, rather than a solution.
  2) Calcium hydroxide is sparingly soluble and a solution is used as limewater
  3) strontium hydroxide is more soluble
  4) barium hydroxide dissolves to produce a strong alkaline solution.

Question 17

Describe the trend in the solubility of the sulfates of group 2 elements as you go down the group

Answer 17

The sulfates of group two elements get less soluble as you go down the group

Question 18

What are the two key uses of barium sulfate- due to it being almost completely insoluble

Answer 18

1) can be taken by mouth as barium meal to outline the gut in X-rays
2) Can be used to test for sulfate ions

Question 19

Describe how barium sulfate is used in X-rays

Answer 19

• barium sulfate can be taken by mouth as barium meal to outline the gut in x-rays
• the test is safe, despite the fact that barium compounds are highly toxic, because barium sulfate is so insoluble.

Question 20

Describe how barium sulfate is used as a simple test for sulfate ions

Answer 20

• the solution is acidified with nitric or hydrochloric acid
• Barium chloride is added to the solution and if a sulfate is present a white precipitate of barium sulfate is formed.

Question 21

Describe the steps in extracting titanium

Answer 21

1. TiO2 (solid) is converted to TiCl4 (liquid) at 900 degrees Celsius
2. The TiCl4 is purified by fractional distillation in an argon atmosphere
3. The Ti is extracted by Mg in an argon atmosphere at 500 degrees Celsius.

Question 22

Why is titanium oxide converted to TiCl4 in order to extract the titanium

Answer 22

Because TiCl4 can be purified by fractional distillation as TiCl4 is molecular (liquid at room temp) rather than ionic like TiO2 (solid at room temp).

Question 23

Why is titanium expensive

Answer 23

1. Magnesium used to extract it is expensive
2. It’s extraction is a batch process which makes it expensive because it is slower and requires more labour and the energy is lost when the reactor in cooled down after stopping.
3. The extraction process is also expensive due to argon and the need to remove moisture (as TiCl4 is susceptible to hydrolysis)
4. High temperatures are required in both steps in its extraction

Question 24

What can we use to remove SO2 from waste gas furnaces by flue gas desulfurisation

Answer 24

Calcium oxide