4.5 - Reactions of Group 2 Elements

• general equation for reaction with water

  M +2H2O → M(OH)2 + H2

  forms a hydroxide which is a base as group 2 metals are alkaline
• trend in reactivity with water

  increases down the group as the energy needed to form positive ions decreases due to a decrease in ionisation energy as electrons get further away from nucleus

  so lower activation energies so faster reactions
• how beryllium reacts with water

  reacts with steam at high temperatures

  doesn't react as much as the others because it has a strong resistant layer of oxide on its surface which lowers its reactivity at lower temperatures
• how magnesium reacts with water

  reacts slowly with cold water but faster with steam - produces magnesium oxide
• how calcium, strontium & barium react with water

  react with cold water with increasing vigour with increasingly less White precipitate because solubility increases
• general equation for reaction with Oxygen


  2M + O2 → 2MO

  all white powders
• how beryllium reacts with oxygen

  only reacts as a powder or dust because it has a strong, thin layer of beryllium oxide on its surface, preventing any new Oxygen from reacting with the rest of it
• how magnesium reacts with oxygen

  burns brightly in air with intense white flame

  so is used in fireworks
• how calcium & strontium react with oxygen


  reluctant at first but then burns brightly with intense white flame with a tinge of red at the end
• how barium reacts with Oxygen

  reacts with a green flame forming a peroxide- BaO2
• formation of peroxides


  when strontium or barium react with oxygen because charge density decreases as ions get bigger so peroxide ions aren't destroyed
• reactions with air


  react with oxygen & nitrogen - produces nitrides
• general equation for reaction with nitrogen

  3X + N2 → X3N2
• Why group 2 elements react with nitrogen

  attraction between 2+ metal ions and 3- nitride ions is big enough to produce very high lattice energies so there's enough energy to break nitrogen-nitrogen bonds so reaction can happen
• reaction with chlorine


  M + Cl2→ MCI

  by heating

  white solid