Group 2, Alkali earth metals

ions formed

2+

Atomic radius increases down group

more electrons

more shells (shielding)

bigger atomic radius

first I.E decreases down group

bigger atomic radius

increased distance between outer electron and nucleus

m.p decreases down group

atomic radius increases

less attraction of e- to nucleus

Mg reaction with water

Mg + 2H2O —> Mg(OH)2 + H2

element reaction with water

Be= does not react Be(OH)2

Mg = very slow Mg(OH)2

Ca = steadily Ca(OH)2

Sr = fairly quick Sr(OH)2

Ba = rapid Ba(OH)2

solubility of compounds

Mg(OH)2 (s) —> Mg(2+) (aq) + 2OH- (aq)

solubilty depends on the negative ion

[OH-] : (least) Mg , Ca, Sr, Ba (most)

[SO4(2-)] : (most) Mg, Ca, Sr, Ba (least)

testing for sulphate ions

BaCl2(aq) + SO4(2-) (aq) —> BaSO4(s) + 2Cl-(aq)

Acidified barium chloride = the acid removes any other ions that could be present

insoluble BaSO4

soluble sulphates

H2SO4 —> SO4(2-) + 2H+

extraction of titanium

TiCl(g) + 2Mg(l) —> Ti(s) + 2MgCl2(l)

extraction of titanium

titanium oxide is first converted to titanium (IV) chloride before being reduced by reaction with Magnesium

This is a displacement reaction

Other uses

Barium sulphate = BARIUM MEALS: barium shows up on x rays unlike soft tissue like the stomach acid and intestines. A barium meal Ba(SO4) is given to medical patients so soft tissues of the digestive system can be examined by x rays

uses : removal of sulphur dioxide

sulphur dioxide is a green house gas which causes acid rain. CaO (calcium oxide) and CaCO3 (calcium carbonate) is used to scrub gases

uses

neutralising acids. They are called the alkali earth metals

commonly used in agriculture to neutralise soil or medicines such as indigestion treatment where they neutralise excess stomach acid