Group 2

• Atomic radius

  Increases down the group

  Down group atoms have more shells of electrons = bigger atom
• Melting points

  Decrease down the group

  Metallic bonding weakens as atomic size increases

  Distance between positive ions and delocalized electrons increases

  Weakened electrostatic attractive
• Ionisation energies

  In all reaction group 2 elements lose their two outer electrons to form ions = 2+

  Element has to undergo to ionisation energies for complete ionisation

  M (g) --> M+ (g) + e-

  M+ --> M2+ (g) + e-

  1st and 2nd decrease down the group

  Less energy to remove the electrons as they become further away from positive nucleus
• Reaction with water

  Metals get more reactive down the group (redox reactions)
• Magnesium hydroxide

  Milk of magnesia = indegestion remedies to nuetralise stomach acid = heart burn

  Water = reacts slowly

  Steam = rapidly = alkaline oxide and hydrogen
• calcium hydroxides

  Calcium reacts the same as Mg but more vigorously

  used to treat acidic soil
• Solubilities of hydroxides

  Increases down the group

  All white solids

  Mg(OH)2 = almost insoluable

  Ca(OH)2 = sparingly soluable used in lime water

  Ba(OH)2 = strongly alkaline solution
• Sulfates

  Decreases down the group

  Barium sulfate = virtually insoluable

  barium meal outlines gut in x ray
• Testing for sulfate ions

  Solutoin acidified with nitric acid or HCL

  Then barium chloride is added

  If a sulfate is present a white precipitate will form

  Acid = removal of carbonate ions

  Barium carbonate is alos white precipiatate = indistinguishable