Group 2 - alkaline earth metals

What happens to atomic radius down group 2 ?

• Increases

What happens to F.I.E down group 2 and why?

• Decreases

• Increased shielding and atomic radius increases

• Outer electron is further from nucleus

What happens to melting point down group 2 and why?

• Decreases

• atomic size increases

• Weaker attraction between positve metal ions and delocalised electrons

• therefore less energy is required to overcome attractions

• (metallic bonding weakens)

What element is an exception for the trend in melting point down group 2 ?

• Calcium

• Its MP is higher than Mg

What happens to reactivity down group 2 and why?

• Increases

• Increased shielding

• Outer electrons further away from nucleus

• Weaker attraction between nucleus and outer electrons - meaning the e^- more easily lost

What is observed when group 2 metals react with water and what is the general equation?

• Effervescence

• Solid metal disappears (gets smaller)

• Metal + 2H₂O → Metal hydroxide + H₂

Which element does not react with water

• Be

What happens to the solubility of metal hydroxides down the group and why?

• Solubility increases

• Size of metal ion increases

• Lattice enthalpy decreases

What is used to test for Mg ions and give equation?

• NaOH

• 2NaOH + MgCl₂ → Mg(OH)₂ + 2NaCl

• Mg(OH)₂ → Will be white ppt

What is Mg(OH)₂ used for?

• Antacid (Indigestion)

• Neutralises excess stomach acid as it has a pH higher than 7

What is Ca(OH)₂ used for?

• Used in agriculture to raise the pH of soil

What are the 2 fully soluble hydroxides?

• Sr(OH)₂

• Ba(OH)₂

What happens to the solubility of metal sulfates down group 2?

• Decreases

What metal sulfate is insoluble?

• BaSO₄

How do test for sulfate ions? and the ionic equation for this reaction

• Use acidified Barium chloride

• If white ppt if formed the ions are present

• The white ppt is BaSO₄

• Ba²⁺ + SO4^2- →BaSO₄

What is BaSO₄ used for and why?

• Used in medicine i.e Barium meals

• Its photo opaque

• It coats the digestive tract

• X-rays get absorbed by BaSO₄

• Allows u see the digestive tract in the same way you see bones

2 uses of G2 elements

• Titanium extraction

• Removal of SO₂ (Flue-gas desulphurisation)

How does titanium extraction work and give equation?

• Mg acts as a reducing agent ( electron donor)

• TiCl₄ + 2Mg → 2MgCl₂ + Ti

• Reaction occurs in a furnace at 1000 degrees

Why does BaCl₂ need to be acidified when testing for sulfate ions?

• To remove carbonate ions

• As they will form also form a white ppt when reacted with BaCl₂

What is SO₂ ?

• Acidic gas

• contributes to acid rain

What 2 compounds can be used to remove SO₂

• CaO

• CaCO₃ (Limestone)

Equation for CaO removing SO₂

Equation for CaCO3 removing SO₂

• CaO + SO₂ →CaSO₃ (calcium sulphite)

• CaCO₃ + SO₂ → CaSO₃ + CO₂

Why is producing calcium sulphite a problem when removing SO₂ ?

• A waste product

• Disposed in landfills