2.2 GROUP 2

atomic radius

increases.

number of shells increases.

melting point

decreases

-ionic radius increases and charge density decreases

-so attraction between +ve ions and delocalised electrons decreases

-so weaker metallic bonding that requires less E.

1st ionisation energy

decreases

-shielding increases

-weaker attraction between the nucleus and the outer electron

g2 + h2O (l) equation

M + 2H2O --> M(OH)2 + H2

(s) (l) (aq) (g)

(s for Mg)

G2 + cold water observations

fizzing

metal dissolving

solution heats up

for calcium, white ppt (less as you go down the group

Mg + H2O (g)

Mg + H2O --> MgO (s) + H2O

white flame, MgO is white powder. Vigorous reaction.

G2 USES- Mg used in titanium extraction

- TiO2 (ore) converted to TiCl4 by heating with C and cl

- this is so TiCl4 (molecular/ (s)) goes thru fractional distillation to be purified.

- Ti extracted by Mg in 1000C furnace.

G2 USES- Ca used in removal of SO2

-Wet scrubbing- dissolve CaO/ CaCO3, spray SO2 on.

-CaSO3 can be used for plasterboards

-SO2 is bad bc reacts w/ wtr/O to make acid rain

G2 USES- Mg, Ca, Ba

-Mg(OH)2 used to neutralise stomach acid

-Ca(OH)2 used to neutralise acidic soil

-BaSO4 used for barium meals, which identifies problems w/ digestive tract by coating lining of soft tissue.

G2 USES- Ba in testing for sulfate ion presence

BaCl2 acidified w/ HCl used as reagent to test sulfate presence.

+ve result = white ppt

HCl is needed to react with CO3 that could form BaCO3 white ppt and give false result. If carbonate present, fizz.

G2 solubility

if anion has double charge (2-), less soluable as you go down group

if anion has single charge (1-), more soluable as you go down group

G2 solubility- Ca(OH)2

Ca(OH)2 = white ppt

Suspension of it in water = more alkaline than Mg(OH)2, bc more soluble.

Ca(OH)2 (aq) = LIME WATER

G2 solubility - Ba(OH)2

Easily dissolves in water.

OH- ions make it strongly alkaline.

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