Group 2- alkaline earth metals

What is the trend in atomic radius?

Atomic radius increases down group 2, as the atoms have more shells/ energy levels, making the atoms bigger

Trend in ionisation energy

Decreases down the group, as the outer electrons are further from the nucleus so held more weakly, meaning the attraction is weaker between nucleus and electron and takes less energy to remove

Trend in melting point

Decreases down the group due to metallic bonding, as the atomic radius increases the distance between the ions and delocalised electrons increases so the electrostatic forces of attraction weaken

What is the reaction of water with steam

Mg + H₂O turns to MgO + H₂- magnesium burns with a bright white flame

Forms magnesium oxide

What is the reaction of magnesium with water?

Mg + 2H₂O turns to Mg (OH)₂ + H₂- slower reaction and no flame

Forms magnesium hydroxide

How do calcium, strontium and barium react with water?

• React with water to form HYDROXIDES (OH)₂ and H₂ gas

What would you observe when reacting a group 2 metal with water?

• Fizzing

• Dissolving of metal

• Temp rise

• Calcium forms a white precipitate

How is magnesium used to extract titanium from TiCl₄?

• Magnesium is more reactive than titanium so can extract it

• Titanium oxide reacts with chlorine to form TiCl4

• TiCl4 is purified via fractional distillation or reduced using sodium

What are the equations involved in the extracting of titanium by magnesium?

• TiO₂ + 2Cl₂ + C turns to TiCl₄ + CO₂

• TiCl₄ + 2Mg turns to Ti + 2MgCl₂

What is the solubility of hydroxides like down the group?

• Solubility increases

• As more hydroxide dissolves, there is a higher concentration of hydroxide ions and so pH will increase down the group

What does magnesium hydroxide do in water?

Sparingly soluble- forms a suspension in water

What does calcium hydroxide do in water?

Partially soluble, dissolves to form limewater which appears as a white precipitate

What does barium hydroxide do in water?

Easily dissolves in water to form a strong alkaline solution

How is magnesium hydroxide used in medicine?

Used to neutralise excess acid in the stomach, acting as a laxative to relieve acid indigestion

How is calcium hydroxide used in agriculture?

Used to raise the pH of soil to neutralise it and make it less acidic

How is calcium oxide and calcium carbonate used to remove SO₂ from flue gases?

• Sulphur dioxide is released in the burning of fossil fuels

• The calcium complex combines with water to create a slurry which is sprayed into the flue gas

• The SO₂ and slurry combine with form calcium sulphite as a waste product

How is barium sulphate (Ba(SO)₄) used in medicine?

• x-rays

• opaque so rays cant pass through and parts of body can appear on x-ray

What is the solubility of the sulphates like down the group?

Solubility decreases

What happens when barium sulphate is in water?

It is insoluble and forms a white precipitate

How is barium chloride used?

• Can be used to test for sulphate ions, as if it is added to a solution containing the ions a white precipitate will form

Why is the barium chloride acidified with hydrogen chloride?

It will remove excess sulphites/ carbonates which may also produce a white precipitate and could mask the results

Why does magnesium have a higher melting point than sodium?

Higher charge density so strong electrostatic forces of attraction between positive ion and sea of delocalised electrons

State what is observed when dilute aqueous sodium hydroxide is added to separate solutions of magnesium chloride and barium chloride.

Magnesium chloride- slight white ppt
Barium chloride- no visible change