Group 2

Physical Properties of Group 2

Size of atoms increase down group 2 because:

• Each element has an extra filled main level of electrons compared to the one above it

Melting points decrease down group 2 because:

• Sea of delocalised electrons get further away from the positive nucleus, therefore the strength of the metallic bond decreases down the group
• Magnesium does not fit this trend as has a different lattice arrangement, that is easier to separate

Ionisation energies decrease down group 2 because:

• Atoms get further from nucleus as we go down the group and there is increased shielding therefore outer electrons are easier to remove.

Metals get more reactive as we go down group 2

Chemical Reactions Of Group 2 Elements- (metals get oxidised)

Reactions with water

Reactions with water show us the metals get more reactive as we go down.

Reaction with cold water produces a hydroxide

Mg(s) + 2H20 (l) --> M(OH)2 (aq) + H2(g)

Reaction with steam produces an oxide

Mg(s) + H20 (g) ---> MgO (s) + H2 (g)

Magnesium reacts slowly with cold water, rapidly with steam

Calcium reacts vigorously even with cold water

Strontium + Barium react very vigorously

Hydroxides

• Hydroxides become more soluble down group 2
• Hydroxides are all white solids
• Magnesium hydroxide (milk of magnesia) is almost insoluble and is used in indigestion remedies to neutralise excess stomach acid
• Calcium Hydroxide is sparingly soluble and is used as lime water
• Strontium hydroxide is more soluble
• Barium Hydroxide, dissolves to produce a strongly alkaline solution

Ba(OH)2 (s) + aq ---> Ba2+ (aq) + 20H- (aq)

Sulfates

• Solubility decreases down the sulfates of group 2.
• Barium sulfate is virtually insoluble. It is used to outline the gut in medical X-rays as the barium atom is good at asorbing xrays. This test is safe despite barium being toxic because it's so insoluble.

The insolubility of barium sulfate is used to test for sulfate ions

• The solution is acidified with nitric/hydrochloric acid (to remove carbonate ions as CO2)
• Barium chloride solution is added
• If a sulfate is present a white precipitate of barium sulfate is formed