Group 2

• What is the general trend in atomic radius down group 2?

  Atomic radius increases

  because there is more shells

  so more shielding

  less attraction between the outermost electron and its nucleus
• What is the general trend in both first and second ionisation energy down group 2?

  ionisation energy decreases down the group

  there is more shells so more shielding

  the outer electron is in a higher energy shell

  increased atomic radius

  outermost electron is further away from the nucleus

  less attraction between the electron and the nucleus
• What is the general trend of melting point down group 2

  melting point decreases

  metallic bonding present

  weak force of attraction between positive metal ions and sea of delocalised electrons

  density of charge decrease
• why does magnesium have a lower melting point than expected in group 2?

  lattice arrangement of atoms is different from elements

  makes it slight easier to separate
• what is the chemical equation for when a metal in group 2 reacts with water?


  metal + 2H20 -> Metal(OH)2 + H2O
• What is the general trend of reactivity down the group?

  reactivity increases

  electron shielding increases

  losing electrons to form a dipositive ion

  outer electrons in the s sublevel are further away from the nucleus of the atom

  outermost electrons are lost easily

  the force of attraction decrease between outermost electrons and nucleus

  atomic radii increase
• Does solubility of group 2 metal hydroxides increase or decrease down the group

  increase
• Is Mg(OH)2 insoluble or soluble or slightly soluble? and what is its equation

  insoluble

  acidic

  white solid

  Mg2+(aq) + 2OH-(aq) -> Mg(OH)2(s)
• Is Ca(OH)2 insoluble or soluble or slightly soluble? and what is its equation

  slightly soluble

  Ca2+(aq)+2OH-(aq) -> Ca(OH)2(S)
• Is Sr(OH)2 insoluble or soluble or slightly soluble? and what is its equation


  Soluble

  no equation
• Is Ba(OH)2 insoluble or soluble or slightly soluble? and what is its equation


  Soluble

  alkaline

  no equation
• What is the use of Magnesium Hydroxide

  Antacid for indigestion relief

  (Milk of Magnesia)

  Mg(OH)2 + 2HCl -> MgCl2 + 2H2O
• What is a use of calcium hydroxide?

  Used in agriculture to neutralise acidic soil

  Ca(OH)2 + H2SO4 -> CaSO4 + 2H2O
• What is the general trend for the solubility of the metal sulphates?

  it decreases down group 2
• Is MgSO4 insoluble or soluble or slightly soluble? and what is its equation

  Soluble

  no equation
• Is CaSO4 insoluble or soluble or slightly soluble? and what is its equation

  Slightly soluble

  Ca2+(aq) + SO42-(aq) -> CaSO4(s)
• Is SrSO4 insoluble or soluble or slightly soluble? and what is its equation

  Insoluble

  Sr2+(aq) + SO42-(aq) -> SrSO4(s)
• Is BaSO4 insoluble or soluble or slightly soluble? and what is its equation

  Insoluble

  Ba2+(aq) + SO42-(aq) -> BaSO4(s)
• What is the use of Group 2 Sulphates?

  medicinal uses

  epsom salts

  mild laxatives

  barium sulphate blocks x-rays
• What is the test for sulphate ions?

  Dilute acid followed by barium chloride or barium nitrate

  if it contains sulphate ions = white precipitate of barium sulphate is formed
• Why is the test solution acidified?

  its acidified with dilute HCL (if using barium chloride) or HNO3 (if using barium nitrate)

  to get rid of unwanted precipitate

  it removes carbonate ions
• What is another use of group 2 metals

  Magnesium in the extraction of titanium from TiCl4

  The use of CaO or CaCO3 to remove SO2 from flue gases
• Describe and explain the atomic radius trend down group 2.

  Atomic radius INCREASES down the group.

  
  

  As you go down a group in the periodic table, the atomic radius gets larger. This is because the extra electron shells are added as you go down the group.
• Describe and explain the first ionisation energy trend down group 2.

  First ionisation energy DECREASES down the group.

  
  

  1. Each element down group 2 has an extra electron shell compared to the one above.

  
  

  1. The extra inner shells shield the outer electrons from the attraction of the nucleus.

  
  

  1. Also, the extra shell means that the outer electrons are further away from the nucleus, which greatly reduced the nucleus's attraction.
• Describe and explain the reactivity trend down group 2.

  Reactivity INCREASES down the group.

  
  

  1. As you go down the group, the first ionisation energy decreases. This is due to the increasing atomic radius and shielding effect.

  
  

  1. When group 2 elements react they lose electrons, forming positive ions. The easier it is to lose electrons, the more reactive the element, so reactivity increases down the group.
• Describe and explain the melting points trend down group 2.

  Melting points generally DECREASE down the group.

  
  

  1. The group 2 elements have typical metallic structures, with positive ions in a crystal structure surrounded by delocalised electrons from the outer electron shells.

  
  

  1. Going down the group the metal ions get bigger. But the number of delocalised electrons per atom doesn't change and neither does the charge on the ion.

  
  

  1. The larger the ionic radius, the further away the delocalise electrons are form the positive nuclei and the less attraction they feel. So it takes less energy to break the bonds, which means the melting points generally decrease as you go down the group. However, there's BIG BLIP at MAGNESIUM because the crystal structure changes.
• Does group 2 elements react with water?

  YES. The react more readily down the group because the ionisation energies decrease.
• What do group 2 metals for when they react with water?

  A metal hydroxide and hydrogen.
• Describe and explain the trend for the solubility of group 2 sulfates.

  The compounds contain DOUBLY charged negative ions so solubility DECREASES down the group.
• Describe and explain the trend for the solubility of group 2 hydroxides.

  INCREASES down the group.
• Why can't titanium be extracted with carbon ore electrolysis?


  Titanium carbonise would form and electrolysis is too expensive and must be very pure.
• Why is Ti expensive?

  Expensive cost of Mg, batch process, Ar is expensive, high temps requires so although abundant, its expensive to extract and so is used to a limited amount.
• What reacts with Group 2 metals with chloride ions to give a white precipitate?

  NaOH
• what is the equation for titanium and magnesium?

  2Mg + TiCl4 → 2MgCl2 + Ti