Summary Notes 3.2.2 - Group 2, the alkaline earth metals

Taylor’s Notes Group 2 Notes

Group Trends
Atomic Radius
Atomic radius increases down the group as the atoms have more shells of electrons, so the atom is bigger

First Ionisation Energy
First ionisation energy decreases down group 2 as atomic radius increases down the group and so the
outer electron being lost is less attracted to the nucleus

Melting point
Alkaline metals exhibit a giant metallic structure

With the exception of Mg, the melting points decrease down the group as the charge density of the metal
ions decreases and so there is a weaker attraction between a sea of delocalised electrons and positive ions
down the group

Reaction of Magnesium with Steam
Magnesium reacts with steam to form Magnesium Oxide and Hydrogen

Mg(s) + H2O(g)  MgO(s) + H2(g)

Reaction of Magnesium with Hot Water
Magnesium reacts with hot water to form Magnesium Hydroxide and Hydrogen

Mg(s) + 2H2O(l)  Mg(OH)2 + H2(g)

Reactions of Group 2 Metals with Cold Water
Calcium, Strontium and Barium react with cold water in the same general reaction

M(s) + 2H2O(I)  M(OH)2(aq/s) + H2(g)

The reaction becomes more vigorous down Group 2 as the First and Second Ionisation Energies decrease
down Group 2

As the Second Ionisation Energies decrease down the group this means that forming the M2+ ion requires
less energy

Extraction of Titanium
Titanium is extracted by a reaction with a more reactive metal (Magnesium)
1. TiO2 (solid) is converted to TiCl4
2. The Titanium in TiCl4 is then displaced by Magnesium

TiO2 + 2Cl2 + C  TiCl4 + CO2 and then TiCl4 + 2Mg  2MgCl2 + Ti

Flue Gas Desulphurisation
Sulphur containing fuels produce sulphur dioxide (SO2) when burnt which contribute to acid rain

This is removed from factory chimneys with basic substances like CaCO3 or CaO

SO2 + CaO  CaSO3 or SO2 + CaO  CaSO3 + CO2