Group 2

• what are all elements in group 2?

  they are all metals, have two outer shell electrons that are both in the S subshell
• what type of reaction is most common with group 2 elements and why?

  redox as they oxidise and lose two electrons to form 2+ions and the other species will be reduced

  therefore are called reducing agents as the metal reduces the other species
• what happens when a group 2 metal reacts with oxygen?

  Forms a metal oxide with the general formula MO as the metal loses two electrons and oxygen gains 2
• what happens when mg burns with O2?

  Magnesium oxide is formed and brilliant white light
• what happens when a group 2 element reacts with water?

  forms an alkaline hydroxide with the general formula M(OH)2 + H2 gas

  more vigorous down the group
• how do group 2 elements react with dilute acid?

  metal + acid —> salt + hydrogen
• how does the reactivity change down group 2?

  Increases

  need to lose two electron- ionisation energy decreases down the group=

  • atomic radius increases so increased shielding
• How do group 2 oxides react with water?

  Hydrolysis- Where they release OH- ions creating metal hydroxide (negative ion and hydroxide)

  eg CaO + H2O —-> CA^2+ + 2OH-

  metal hydroxide - CA(OH)2
• Are group 2 metal hydroxides soluble?

  Only slightly but more saturation = forms solid precipitate

  • solubility of hydroxides increase down a group therefore solutions become more alkaline become more OH- concentration
• how and why are group 2 compounds used in agriculture?

  Calcium hydroxide is used to increase Ph of acidic soils eg white lime powders

  the OH- ions neutralise the acid in the soil forming water
• how and why are group two compounds used in medicine?

  group 2 bases in antacid= treat acid indigestion

  • use calcium or magnesium carbonate which neutralise the hydrochloride acid in the stomach
  • eg Mg(OH)2 +2HCL —> MgCl2 + H2O