Group 2

• General and physical properties

  • Occur in nature in combination with other elements due to their high reactivity
  • Show an oxidation state of +2 by losing two electrons in the outer shell
  • Atomic radius increases down the group
  • The melting point decreases down the group as the ionic radius increases of the cations
• Thermal decomposition of group 2 nitrates 


  General equation

  -M(No3)2 -> MO(s) + NO2(g) + 1/2O2(g)

  -White solid oxide formed, brown fumes of nitrogen gas and colorless oxygen gas

  Example: Mg(No3)2 --> MgO + No2 + 1/2O2

  Thermal stability of group 2 nitrates increases down the group
• Thermal decomposition of group 2 carbonates

  • General equation
  • MCO3(S) --> MO(S) + CO2(g)
  • Example: MgCo3 --> MgO(s) + Co2 (g)
  • Thermal stability of group 2 carbonates increases down the group
• Thermal stability of group 2 carbonates

  Thermal stability increases down the group as the cationic radius increases down the group and the charged density decreases which in turn decreases the polarising power of the cation which is not able to distort the electron cloud of the carbonate anion effectively therefore higher temperatures are needed to decompose them.
• Uses of Group 2 compounds

  • MgO - Refractory material in blast furnaces (Strong bonding and high melting and boilin boiling point)
  • CaO (solid) - lime or quick lime
  • Ca(OH)2 (solid) - slaked lime
  • Ca(OH)2 (aq) - Limewater
  • CaCo3 (Solid) - Limestone
• Group 2 metals + Oxygen

  • 2Mg + O2 --> 2MgO (Intense white flame)
  • 2Ca + O2 ---> 2CaO (Brick red flame)
  • 2Sr + O2 --> SrO (White/Crimson flame)
  • 2Ba + O2 --> BaO (apple green flame)
• Reaction of Group 2 Oxides (With water)

  • Beo is amphoteric and insoluble in water
  • MgO + H2O --> Mg(OH)2 + H2(Not very soluble, pH 11)
  • CaO + H2O --> Ca(OH)2 + H2(Not very soluble Ph, 9)(Observations are Calcium sinks to the bottom, fizzing and water turns milky)
  • SrO + H2O --> Sr(OH)2 + H2 soluble pH, 13
  • BaO + H2O --> Ba(OH)2 + H2 soluble pH, 13
  • Group 2 hydroxides become more soluble down the group
• Reaction of group 2 metals with acids

  • All group 2 oxides are basic and react with acids to form salt and water
  • General equation: MO + 2HCL --> MCL2 + H2O
  • General equation: MO + H2SO4 --> MSO4 + H2O
  • Solubility of group 2 sulfites decreases down the group
• Trend in reactivity

  The reactivity of group 2 metals increases down the group as the atomic radius increases, the sea of delocalized electrons is further away from the nucleus, and there is more shielding effect due to which they experience a weaker nuclear force of reaction between the cations and sea of delocalized electrons.