Group 2

What is the trend in melting point of the group 2 metals?

• Generally decreases down the group

• Atomic radius increases so weaker attraction between positive metal ions and sea of delocalised electrons

What is metallic bonding?

Bonding occurring between a lattice of positive metal ions and a sea of delocalised electrons

What is the general equation for the reaction of group 2 metals with cold water?

M_(s) + 2H₂O_(l) → M(OH)₂ + H₂

What is the trend in reactivity of group 2 metals?

• Reactivity increases

• Atomic radius and shielding increase

• Attractive force between outer electrons and positive nucleus decreases, so electrons are more easily removed

What do we observe when reacting group 2 metals with cold water?

• Mg- Reacts very slowly, tiny bubbles

• Ca- Fizzes steadily

• Sr- reacts more vigorously than Ca, fizzes rapidly, metal disappears quickly

• Ba- Most vigorous, rapid bubbling, metal disappears quickly

How does magnesium react with steam?

• Reacts faster

• Burns with a bright white flame

What is the symbol equation for the reaction of Magnesium with steam?

Mg_(s) + H₂O_(g) → MgO_(s) + H_2(g)

What is the trend in solubility and alkalinity of the group 2 metal hydroxides?

• Both increase

• Magnesium is sparingly soluble in water while barium is very soluble

How can we test for Mg²⁺ or Ca²⁺ ions and write the ionic equation for this test?

• Add NaOH or OH^- ions

• White precipitate forms

• M²⁺ _(aq) + 2OH^- _(aq) → M(OH)_{2 (s)}

What is the general ionic equation for the dissociation of a metal hydroxide in water and what can we see from this?

• M(OH)_{2 (s)} ⇌ M²⁺ _(aq) + 2OH^- _(s)

• The more soluble a hydroxide is, the more equilibrium moves to the right

• This increases the concentration of OH^- ions which increases the pH

How can we test for the presence of Barium and sulphate ions and write the ionic equation for this test

• Add BaCl₂ solution

• White precipitate forms

• Ionic equation: Ba_²+(aq)+SO₄²⁻​(aq)⟶BaSO_4​(s)

What is the trend of solubility in group 2 sulphates

Decreases

What can Magnesium hydroxide be used for and write an equation for this use

• Indigestion medicine (milk of magnesia)

• Used as a laxative, relieving indigestion

• Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O

What can calcium hydroxide be used for?

• Agriculture (soils)

• Raises the pH of soil

What can barium sulphate be used for?

• X-raying digestive system

• Used to coat the inner lining of the intestines and absorbs a lot of radiation

Why can barium sulphate be used for X-rays despite being toxic?

The solubility of Barium Sulphate is too low so hardly any Ba²⁺ ions are present in solution

What can magnesium be used for in mining and state any related equations

• The extraction of titanium from TiCl₄

• Rutile ore (TiO₂) is converted to TiCl₄ at 900^oC

  • TiO₂ + 2Cl₂ + 2C → TiCl₄ + 2CO

• Ti is then displaced by magnesium which is more reactive

• TiCl₄ + 2Mg → Ti + 2MgCl₂

What can calcium oxide/calcium carbonate be used for?

• Flue gas desulphurisation

• Neutralises acid SO₂