1. Group 2 Elements & Compounds
Trends in Chemical Properties

2. Reactivity increases down the group
Reaction with Water Be
Does not react Mg
Slowly with cold water
Reacts readily with steam
Mg(s) + H2O(g) → MgO(S) + H2(g) Ca
All react with cold water
Increasing reactivity
Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g) Sr
Sr(s) + 2H2O(l) → Sr(OH)2(aq) + H2(g) Ba
Ba(s) + 2H2O(l) → Ba(OH)2(aq) + H2(g)
Reactivity increases down the group
No of energy levels increases down group
Outer “s” e- further from nucleus
More easily lost

3. Metal Hydroxides Mg(OH)2 Sparingly Soluble
(only a v small amount dissolves)
Milk of Magnesia
Ca(OH)2
Slightly soluble
Limewater
Sr(OH)2
Soluble
Ba(OH)2
Milk of Magnesia
suspension of Mg(OH)2 in water taken to neutralise acid indigestion .
Very weak alkali
Excess doesn’t disturb digestion (sparingly soluble)

4. Solubility increases down the group
Metal Hydroxides
Mg(OH)2
Sparingly Soluble
(only a v small amount dissolves)
Solubility increases down the group
Ca(OH)2
Slightly soluble
Sr(OH)2
Soluble
Ba(OH)2
MgCl2(aq) + 2NaOH(aq) → Mg(OH)2(s) + 2NaCl(aq)
white precipitate
BaCl2(aq) + 2NaOH(aq) → Ba(OH)2(aq) + 2NaCl(aq)
no precipitate

5. Metal Sulphates MgSO4 Very Soluble Epsom Salts (laxative) CaSO4
Sparingly soluble
SrSO4
Insoluble
BaSO4
Very Insoluble
Barium Meal
Barium Sulphate – extremely insoluble in water
BaSO4 is opaque to X rays
Suspension of BaSO4 given to patients with digestive problems
X-ray will highlight problems

6. Solubility increases up the group
Metal Sulphates
MgSO4
Very Soluble
Solubility increases up the group
CaSO4
Sparingly soluble
SrSO4
Insoluble
BaSO4
Very Insoluble
MgCl2 (aq) + Na2SO4(aq) → MgSO4(aq) + 2NaCl(aq)
no precipitate
BaCl2(aq) + 2NaSO4(aq) → BaSO4(s) + 2NaCl(aq)
white precipitate

7. Test for Sulphate ions Add dilute nitric acid
(this prevents the formation of unwanted precipitates)
Add few drops of Barium nitrate Or
Add dilute hydrochloric acid
Add few drops of Barium chloride

8. Test for Sulphate ions BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)
white precipitate
If sulphate ions are present in solution a white ppt of barium sulphate will form.
Ba(NO3)2(aq) + 2KSO4(aq) → BaSO4(s) + 2KNO3(aq)