3.2.2 Group 2, The Alkaline Earth Metals

Question 1

Group 2 elements lose __ electrons when they react

Answer 1

2

(all end s² & make 2+ ions)

Question 2

Atomic Radius _____ Down the Group

Answer 2

Increases

Question 3

Why does atomic radius increase down the group? (3)

Answer 3

• Number of shells increase
  
  • More distance between nucleus and outer electrons
• Outer shells more shielded
• Less attraction between nucleus and outer electrons

Question 4

First Ionisation Energy ______ Down the Group

Answer 4

Decreases

Question 5

Explain why first ionisation energy decreases down the group (4)

Answer 5

• Number of shells increase
  
  • Increased distance between nucleus and outer electrons
• Outer shells more shielded
• Less attraction between nucleus and outer electrons
• Easier to remove outer electron = less energy

Question 6

Reactivity ______ Down the Group

Answer 6

Increases

Question 7

Explain why reactivity increases down the group

Answer 7

1. First ionisation energy decreases down group
   
   • Due to increasing atomic radius and shielding effect
2. When Group 2 elements react = lose electrons & form positive ions
   
   • Easier it is to lose electrons (i.e. the lower the 1st and 2nd ionisation energies) = more reactive the element
   • So reactivity increases down group

Question 8

Melting Points _______ _______ Down the Group

Answer 8

Generally Decrease

Question 9

Describe Group 2 elements’ structure

Answer 9

• Metallic structures
  
  • Positive ions in crystal structure surround by delocalised electrons from outer electron shells

Question 10

Why do melting points generally decrease down the group? (4)

Answer 10

• Size of positive ion increases, but charge remains the same
• Delocalised electrons further away from positive ions
• Weaker electrostatic forces of attraction between positive ions and delocalised electrons
• Weaker metallic bonds = less energy needed to break

Question 11

Where is there a big ‘blip’ at magnesium?

Answer 11

∵ crystal structure (arrangement of metallic ions) changes

Question 12

Group 2 Elements React with ____

Answer 12

Water

Question 13

When they react with water, they are oxidised from start of ____ to ____ forming ____ ____

Answer 13

When they react with water, they are oxidised from start of 0 to +2 forming M²⁺ ions

Question 14

When Group 2 metal react with water, what 2 products do they give?

Answer 14

Metal hydroxide and hydrogen

Question 15

Group 2 Elements React with Water

State the general symbol equation

Answer 15

Question 16

Group 2 metals react ___ _____ down the group

Answer 16

more readily

Question 17

Why do Group 2 metals react more readily down the group?

Answer 17

∵ ionisation energies decrease

Question 18

Solubility Trends depend on ______ ___

Answer 18

Compound Anion

Question 19

State the 2 general solubility trends of Group 2 elements

Answer 19

1. Generally, compounds of Group 2 elements that contain singly charged negative ions (e.g. OH^-) ↑ in solubility down group
2. Compounds that contain doubly charged negative ions (e.g. SO₄^-2) ↓ in solubility down group

Question 20

Fill in the gaps

Answer 20

Question 21

What are compounds like magnesium hydroxide, which have very low solubilities said to be?

Answer 21

Sparingly soluble

Question 22

Barium sulfate is _____ in water

Answer 22

insoluble

Question 23

Describe the test for sulfate ions (SO₄^2-)

Answer 23

1. Add dilute hydrochloric acid and then barium chloride solution, BaCl_2(aq)
2. If white precipitate of barium sulfate forms = original compound contained sulfate

Question 24

Test for sulfate ions

Why should you acidify the solution?

Answer 24

To get rid of any lurking sulfites or carbonates which will also produce a white precipitate

Question 25

What are Group 2 compounds used for?

Answer 25

To neutralise acidity

Question 26

Name 2 common examples of Group 2 compounds that are used to neutralise acidity

Answer 26

• Calcium hydroxide (slaked lime, Ca(OH)₂)
• Magnesium hydroxide (Mg(OH)₂)

Question 27

What is calcium hydroxide used for?

Answer 27

In agriculture to neutralise acidic soils

Question 28

What is magnesium hydroxide used for?

Answer 28

• Used in indigestion tablets as an antacid
• Substance which neutralises excess stomach acid

Question 29

State the ionic equation for neutralisation, include the state symbols

(for both Ca(OH)₂ & Mg(OH)₂)

Answer 29

H⁺_(aq) + OH^-_(aq) → H₂O_(l)

Question 30

What is barium sulfate is used in?

Answer 30

‘Barium Meals’

Question 31

Barium sulfate is ______ to X-rays

Answer 31

Barium sulfate is opaque to X-rays - won’t pass though it

Question 32

What are ‘barium meals’ used to help?

Answer 32

Diagnose problems with oesophagus, stomach or intestines

Question 33

Describe how ‘barium meals’ are used

Answer 33

1. Patient swallows barium meal
2. Barium sulfate coats tissues, making them show up on X-rays, showing structure of organs

Question 34

What is magnesium used for?

Answer 34

To extract titanium from its ore

Question 35

Describe how magnesium is used to extract titanium from its ore

Answer 35

1. Main titanium ore (TiO₂) is converted to titanium(IV) chloride (TiCl₄) by heating it with carbon in steam of chlorine gas
2. Titanium chloride is then purified by fractional distillation
3. Then reduced by magnesium in furnace at 1000°C

Question 36

Represent how magnesium is used to extract titanium from its ore by writing an equation

Answer 36

Question 37

What is wet scrubbing?

Answer 37

When acidic sulfur dioxide is removed from flue gases by reacting with an alkali

Question 38

Name 2 substances that can be used to remove sulfur dioxide from flue gases

Answer 38

Powdered calcium oxide (CaO, lime) and calcium carbonate (CaCO₃, limestone)

Question 39

Describe how calcium oxide and calcium carbonate is used to remove sulfur dioxide from flue gases

Answer 39

1. Slurry is made by mixing calcium oxide or calcium carbonate with water
2. The sprayed onto flue gases
3. Sulfur dioxide reacts with alkaline slurry and produces solid waste product, calcium sulfite

Question 40

Represent how calcium oxide is used to remove sulfur dioxide from flue gases by using an equation

Answer 40

Question 41

Represent how calcium carbonate is used to remove sulfur dioxide from flue gases by using an equation

Answer 41

Question 42

Explain why it’s possible to use barium sulfate in barium meals even though barium ions are poisonous

Answer 42

Barium sulfate is insoluble ∴ non-toxic

Question 43

Explain why the electronegativity values of Group 2 elements Be-Ba decrease down the group (2)

Answer 43

• Increases in no. of shells/increased sheilding
• Decreased attraction for bonding electrons

Question 44

Write the ionic equation, with state symbols, to show the reaction of calcium with an excess of water

Answer 44

Ca_(s) + H₂O_(l) → Ca²⁺_(aq) + 2OH^-_(aq) + H_2(g)

Question 45

Magnesium reacts rapidly with ___

Answer 45

steam

Question 46

State two observations made when magnesium reacts with steam (2)

Answer 46

• White light
• White powder

Question 47

Write the equation for when magnesium reacts with steam

Answer 47

Mg + H₂O → MgO + H₂