Group 2- Alkaline Earth Metals

Atomic Radius
1. INCREASES down group
First Ionisation Energy
1. DECREASES down group
  1. increasing nuclear distance
  2. increasing shielding
Reactivity
1. INCREASES down group
  1. decreasing Ionisation Energy so electrons are lost more easily
Melting Point
1. DECREASES down group
  1. metallic structure
  2. larger ions so delocalised electrons are less attracted to nucleus, so less energy to break bonds
Reactions with Water
1. M + 2H2O --> M(OH)2 + H2
  1. EXCEPTION: Magnesium will ALSO react with steam to form MgO and Hydrogen
2. react more readily down group because ionisation energies decrease
Solubility
1. single-charge anion (HYDROXIDE)
  1. INCREASES down group
2. double-charge anion (SULFATE)
  1. DECREASES down group
3. Test for Sulfate Ions
  1. add acidified Barium Chloride
    1. white precipitate indicates presence of sulfate ions
Applications
1. Neutralisers
  1. Ca(OH)2 - slaked lime - used in agriculture
  2. Mg(OH)2 - antacid
  3. ionic equation: H+ + OH- --> H2O
2. Barium Meals
  1. use Barium Sulfate
  2. shows up on X-Rays
3. Magnesium
  1. extracts Titanium
  2. Titanium ore (TiO2) is converted to TiCl4 by heating with carbon in stream of chlorine gas
  3. Purified by fractional distillation
  4. reduced by Mg in 1000C furnace
4. Removing SO2
  1. CaO + H2O + SO2 --> CaSO3 + 2H2O
  2. CaCO3 + 2H2O + SO2 --> CaSO3 + 2H2O + CO2
  3. WET SCRUBBING - mix powdered CaO or CaCO3 with water then spray on flue gases to produce solid waste product

Resource summary

	Created by Eleanor H almost 8 years ago