Reactivity Trends

• what is the trend in the melting point in group 2 elements 


  the melting point of group 2 elements generally decreases down the ground apart from magnesium.
• why do melting points generally decrease down group 2 


  • the ionic radius of the metal ion increases
  • the delocalised electrons get further away from the positive nuclei
  • meaning these is a weaker electrostatic attraction between the delocalised electrons and the positive nuclei
  • so the amount of energy needed to break the metallic bonds decreases
• why is magnesium not similar to the trend in melting point of group 2 elements 


  the magnesiums anomaly occurs because it forms an unusually stable crystal structure.
• what is the trend in ionisation energy down group two


  the first ionisation energy shows an overall decrease going down the group. the energy is a measure of the strength of electrostatic attraction between the outer electron and the nucleus.
• why does ionisation energy decrease down the group 


  • nuclear charge - increases down the group as more protons are added therefore increasing the electron attraction
  • atomic radius - increases down the group as more electron shells are added moving electrons away from the nucleus
  • electron shielding - increases down group as more inner electron shells reduce nuclear attraction.

  the atomic radius and shielding effects down group 2 are greater than the effect of the nuclear charge. leading to an overall decrease in ionisation energies
• trend in reactivity down group 2 


  reactivity decreases down group 2. this is because it becomes easier to remove electrons further down the group. the reactions with elements such as water oxygen and acids become more vigorous as you descend down the group.
• reaction with water 


  reaction of a group 2 metal with cold water produces a metal hydroxide and hydrogen gas.
• what is the reactivity trends of the group 2 earth metals with water?


  Be - no reaction

  Mg - reacts slowly

  Ca - steady reaction rate

  Sr - reacts fairly quick

  Ba - rapid reaction.