Group 2

• What block are group 2 elements part of and why ?

  S block because the outer most electrons are in an s subshell
• Describe and explain the trends in atomic radii of the Group 2 elements Mg to Ba.


  The atomic radius increases down the group because the number of shells increases so shielding increases. Therefore the nuclear attraction between the nucleus and the outer electrons decreases. The increase in nuclear charge is outweighed by size and shielding.
• Explain the first ionisation energies of Group 2 elements, Mg to Ba.


  The ionisation energies decrease down the group because the atomic radius increases due to the increase of shells and shielding also increases. The nuclear attraction between the nucleus and the outer electrons decreases, therefore less energy is required to remove the outer electrons. The increase in nuclear charge is outweighed by size and shielding.
• Are Group 2 elements oxidised or reduced ?

  oxidised
• Is oxidation gain or loss of electrons ?

  loss
• Is reduction gain or loss of electrons ?

  gain
• Write the half equation for the oxidation of Mg.

  Mg --> Mg*2+ + 2e-
• Explain in terms of NASA, why the reactivity of Group 2 elements increases down the group ?

  As you go down the group the atomic radius increases because the number of shells increases this means shielding increases because the are more inner shell electrons. The increase of nuclear charge is outweighed by these two factors. Therefore the nuclear attraction between the nucleus and the outer electrons decreases. As a result the ionisation energy decreases as less energy is needed to remove electrons.
• Procedure for reaction of G2 elements with Oxygen .

  1. Using metal tongues, burn a strip of Mg ribbon.
• Observations for reaction of G2 elements with Oxygen.


  Bright white light and white/grey powder
• What is the overall equation for reaction of G2 elements with Oxygen ? (use M to show G2)

  2M (s) + O2(g) --> 2MO (s)
• Are G2 elements oxidised or reduced ?

  Oxidised
• Do G2 elements gain or lose electrons ?

  Lose
• Do G2 elements oxidation states increase or decrease and by how much ?

  Increase by 2
• Procedure for reaction of G2 elements with water.

  1. Add water to a test tube and place a strip of Mg into the test tube.
  2. Note any observations after 15mins.
  3. Add water to a second test tube and place a granule of Ca inro the test tube.
  4. Collect the gas with an inverted, clean and dry test tube.
  5. Test the gas collected with a lit splint.
• Observations for reaction of G2 elements with water.

  Mg: no observation at the beginning, a small amount of effervescence after 15mins

  Ca: effervescence, hydrogen gas = squeaky pop
• What is the overall equation for the reaction of G2 elements with water ? (use M to show G2)


  M(s) + 2H2O(l) --> M(OH)2(aq) + H2(g)
• Procedure for the reaction of G2 oxides with water.

  1. Add water to a test tube and place a spatula of CaO into the water.
  2. Shake the solution.
  3. Add 2-3 drops of universal indicator solution.
  4. Note the colour change.
• Observations for the reaction of G2 metal oxides with water.

  Universal indicator turns blue

  pH = weakly alkali 9-12
• What is the overall equation for the reaction of G2 oxides with water ? (use M to show G2)



  MO(s) + H2O(l) --> M(OH)2(aq)
• Procedure for the reaction of G2 elements with dilute acids.

  1. Add 10cm3 of Hcl into a test tube and add a strip of Mg to the acid.
  2. Note any observations.
  3. Add 10cm of HCl to a second test tube and add a granule of Ca to the acid.
  4. Collect the gas using an inverted clean and dry test tube and test with a lit splint.
• Observation for the reaction of G2 element with dilute acid.

  Mg: effervescence and Mg dissolves

  Ca: more vigorous effervescence, Ca dissolves and Hydrogen gas = squeaky pop
• What is the overall equation for the reaction of G2 elements with dilute acid ? (use M to show G2)



  M(s) + 2HCl(aq) --> MCl2(aq) + H2(g)
• Does the alkalinity of G2 elements increase or decrease down the group ?

  Increase
• Does the solubility of hydroxides increase or decrease down G2 ? What does this result in ?

  Increase, this means solutions contain mor OH- ions and are more alkaline
• What are the trends going down G2 hydroxides ?

  Solubility increases, pH increases and alkalinity increases
• Describe the test used to show the solubility of hydroxides.


  1. Add a spatula of each G2 oxide to water in a test tube.
  2. Shake the mixture. As there will be insufficient water, some of the metal hydroxides will dissolve so there will be some white undissolved solid.
  3. Measure the pH of each solution.
• State and explain the trend in alkalinity of the solution formed when group 2 oxides are added to water.

  As you go down group 2, MO reacts with water to form M(OH)2. The solubility of M(OH)2 increase and the concentration of OH-(aq) increases. Therefore the pH increases and this means the alkalinity increases.
• What is the use of Ca(OH)2 ? How ? Equation.

  Use: regulates the acidity of soils

  How: neutralises the acidic soils, water is formed

  Equation: Ca(OH)2(s) + 2H+(aq) --> Ca2+(aq) + H2O(l)
• What is the use of Mg(OH)2 and CaCO3 ? How ? Equation.

  Use: used as antacids for treating acid indigestion

  How: neutralises stomach acidity

  Equation: Mg(OH)2(s) + 2HCl(aq) --> MgCl2(aq) + 2H2O(l)

  CaCO3(s) + 2HCl(aq) --> CaCl2(aq) + H2O(l) + CO2(g)
• Word equation for thermal decomposition.

  Metal carbonate --> metal oxide + carbon dioxide
• hydroxide + acid -->

  salt + water
• oxide + acid -->


  salt + water
• metal + acid -->

  hydrogen + salt
• metal + water -->

  metal hydroxide + hydrogen
• metal + oxygen -->

  oxide