Group 2: the alkaline earth metals -2

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  • Created by: Shannon
  • Created on: 26-03-15 10:31
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  • Group 2: the alkaline earth metals
    • Ionisation energies
      • First ionisation energy
        • The energy change when one mole of atoms of an element in a gaseous state loses on electron to form one mole of positive ion
        • General trend
          • Decreases down the group
            • Progressively easier to remove an outer electron due to an increase in atomic radius
              • More shielding from attraction of nucleus
      • Second ionisation energy
        • The energy change when one mole gaseously 1+ ions loses one mole of electrons to form one mole of 2+ ions.
      • Third ionisation energy
        • Trend
          • Big increase in value for ionisation energy - removing electron from a subshell closer to the nucleus
    • Reaction with oxygen
      • Burn in oxygen to form solid metal oxides
      • Reactivity increases down the group
    • Reaction with chlorine
      • Burn in chlorine gas to form solid metal chlorides
      • Reactivity increases down the group
    • Reaction with water
      • React with water to form either oxides or hydroxides
      • Reactivity increases down the group
      • Magnesium - produces oxide Mg + H2O -> MgO + H2
      • Ca, Sr & Ba produce hydroxides
        • e.g Ca + H2O -> Ca(OH)2 + H2
    • Reactions of group 2 oxides
      • Water
        • Mg reacts only slightly
        • Ca, Sr & Ba react to form metal hydroxide
      • Dilute acid
        • Form metal chloride salt and water
    • Reactions of group 2 hydroxides
      • Dilute acid
        • Form metal chloride salt and water
    • Solubility
      • Hydroxides
        • Increases down the group
        • Calcium hydroxide used in water treatment
      • Sulfates
        • Decreases down the group
        • Barium sulfate used in xrays
    • Flame colours
      • Visible due to the movement of electrons
        • Electrons gain energy, moving to higher orbitals
          • Returning to ground state emits light energy
      • Characteristic colours
        • Li = Red
        • K = lilac
        • Ca = orange/red
        • Cs = blue/violet
        • Sr = brick red
        • Ba = pale green

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