Group 2 elements:

• General characteristics:

• Physical properties:

  • Silvery-white, lustrous metals
  • Low density
  • Soft and malleable
  • Low melting and boiling points

• Chemical properties:

  • Highly reactive
  • Readily lose two electrons to form stable 2+ ions
  • Form basic oxides and hydroxides
  • React with water to produce hydrogen gas
  • Form ionic halides
  • Can reduce metal oxides

• Electronic configuration:

• All group 2 elements have two electrons in their outermost energy level (ns2)

• Atomic and ionic radii:

• Atomic radii increase down the group

• Ionic radii are smaller than atomic radii

• Ionization enthalpy:

• Ionization enthalpies decrease down the group

• Hydration enthalpy:

• Hydration enthalpies decrease down the group

• Oxidation states:

• All group 2 elements have a +2 oxidation state

• Reactions with:

• Oxygen:

  • React with oxygen to form oxides, e.g. CaO

• Hydrogen:

  • React with hydrogen to form hydrides, e.g. CaH2

• Water:

  • React with water to produce氢气, e.g. Ca + 2H2O -> Ca(OH)2 + H2

• Halogens:

  • React with halogens to form halides, e.g. CaCl2

• Metal carbonates:

  • React with metal carbonates to form basic carbonates, e.g. CaCO3 + Na2CO3 -> CaCO3·Na2CO3

• Preparation and properties of some important compounds:

• Oxides:

  • Basic oxides
  • React with water to form hydroxides

• Hydroxides:

  • Strong bases
  • React with acids to form salts

• Halides:

  • Ionic compounds
  • Soluble in water

• Carbonates:

  • Basic carbonates
  • Decompose on heating to form oxides and carbon dioxide

• Sulphates:

  • Ionic compounds
  • Soluble in water

• Applications of group 2 elements and their compounds:

• Calcium:

  • Used in the production of cement, plaster, and glass

• Magnesium:

  • Used in the production of alloys, such as magnesium-aluminium alloy

• Strontium:

  • Used in the production of fireworks and flares

• Barium:

  • Used in the production of X-ray contrast agents and television screens