Group 2 Alkaline Earth Metals

What is the trend in first ionisation energy down Group 2?

Decreases because outer electrons are further from the nucleus and more shielded

What is the trend in melting points down Group 2?

Decreases due to weaker metallic bonding as ionic radius increases

What is the general reaction of Group 2 metals Mg–Ba with water?

M + 2H₂O → M(OH)₂ + H₂

How does magnesium react with cold water?

Very slowly, makes Mg(OH)₂

How does magnesium react with steam?

Vigorously: Mg + H₂O(g) → MgO + H₂

What is observed when calcium reacts with water?

Effervescence, white precipitate of Ca(OH)₂ forms, solution becomes cloudy

Why does reactivity increase down Group 2?

Ionisation energies decrease, making it easier to lose electrons

What is the general reaction of Group 2 metals with dilute hydrochloric acid?

M + 2HCl → MCl₂ + H₂

What is the trend in solubility of Group 2 hydroxides down the group?

Increases down the group

What is the solubility of magnesium hydroxide?

Sparingly soluble

What is the trend in alkalinity of Group 2 hydroxide solutions down the group?

Increases down the group as solubility increases, producing more OH⁻ ions

What is magnesium hydroxide used for?

In medicine as an antacid to neutralise excess stomach acid

What is calcium hydroxide used for?

In agriculture to neutralise acidic soils

What is the ionic equation for neutralisation by Group 2 hydroxides?

H⁺ + OH⁻ → H₂O

What is the trend in solubility of Group 2 sulfates down the group?

Decreases down the group

What is the test for sulfate ions?

Add dilute HCl followed by barium chloride solution; white precipitate of BaSO₄ forms

Why is the BaCl₂ solution acidified when testing for sulfates?

To remove carbonate and sulfite ions that would also form precipitates with Ba²⁺ and give false result

Write the ionic equation for the sulfate test.

Ba²⁺ + SO₄²⁻ → BaSO₄(s)

What is barium sulfate used for in medicine?

As a barium meal for X-ray imaging of the digestive system bc it’s dense and absorbs x-rays

Why is BaSO₄ safe to ingest but Ba²⁺ ions are toxic?

BaSO₄ is insoluble so passes through the gut without releasing toxic Ba²⁺ ions into the blood

What is magnesium used for industrially?

In the extraction of titanium from TiCl₄

Write the equation for magnesium in titanium extraction.

TiCl₄ + 2Mg → Ti + 2MgCl₂

What is the use of calcium oxide or calcium carbonate?

To remove SO₂ from flue gases (flue gas desulfurisation) through wet scrubbing

Write the equation for calcium oxide with sulfur dioxide.

CaO + SO₂ → CaSO₃

Write the equation for calcium carbonate with sulfur dioxide.

CaCO₃ + SO₂ → CaSO₃ + CO₂

What is the environmental benefit of flue gas desulfurisation (wet scrubbing)?

Reduces acid rain by removing SO₂ from emissions

What is the general reaction of Group 2 hydroxides with dilute hydrochloric acid?

M(OH)₂ + 2HCl → MCl₂ + 2H₂O

What’s the first step and equation of titanium extraction before the compound is reduced using magnesium?

React TiO₂ ore with carbon and chloride TiO₂ + 2Cl₂ + 2C —> TiCl₄ + 2CO

Why can’t titanium be extracted from its ore with carbon like other metals?

It makes titanium carbide TiC which is brittle and useless.

Why’s magnesium oxide safer than sodium oxide as treatment for indigestion?

Magnesium hydroxide is less soluble so it releases less OH^- ions, doesn’t increase pH too much