Developing metals

• transition metal: an element (d-block) which forms at least one stable ion with a partially filled d-subshell
• physical properties of transition metals: high melting and boiling points , high densities , slightly low atomic radius
• Why isn't scandium a transition metal? Sc3+ ion loses 3e to then have an empty d subshell (Sc does not form a stable ion with a partially filled d-subshell)
• Why isn't zinc a transition metal? Zn2+ loses 2e to then have a full d subshell (so Zn doesn't form a stable ion with a partially filled d-subshell)
• What loses electrons first, the 4s-subshell or the 3d-subshell? 4s-subshell
• chemical properties of transition metals: variable oxidation states , coloured ions in solution
• what is special about chromium/ why does chromium not follow the electron configuration pattern? -one electron in each d orbital and 1 electron in 4s subshell to increase stability/

  
  

  -electron jumps from 4s-subshell to 3d-subshell in order (they have similar energy levels) in order to make it more stable
• what is special about copper/ why does copper not follow the electron configuration pattern? -prefers one full 3d-subshell and one electron in 4s-subshell/

  
  

  - electron jumps from 4s-subshell to 3d-subshell in order to make it more stable (full d-subshell is more stable
• manganate redox titration: 5Fe+ + Mn04- + 8H+ ----> 5Fe3+ + Mn2+ + 4H20
• manganate redox titration colour change: colourless to permanent pink colour
• why is no indicator used in the Mn redox titration: Mn04- produces its own permanent pink colour
• Heterogenous catalysis: Transition metals use the 4s and 3d electrons of the atoms on metal surface to form weak bonds (known as chemisorption) to reactants. Once the reaction has occurred, the bonds break to release the products.

  
  

  E.g.

  1. reactants adsorb to surface of catalyst

  2. Bonds weaken and break

  3. new bonds form

  4 products desorb from catalyst surface
• homogenous catalysis: -Transition metal ion catalyses reaction in its aqueous phase.

  
  

  -The transition metal then forms an intermediate compound which breaks down to form products.

  
  

  - Catalyst is always reformed afterwards
• homogenic catalytic action of cobalt: 1. reactants (2,3 -dihydroxybutanoate ions and hydrogen peroxide - contains CO2+ (pink)

  
  

  2. intermediate - contains CO3+ (green)

  
  

  3. products (Carbon dioxide, methanoate and water- contains CO2+ (pink)
• Fe2+ colour in aqueous solution


  green
• Fe3+ colour in aqueous solution


  orange/brown
• Cu+ colour in aqueous solution


  unstable in aqueous solution
• Cu2+ colour in aqueous solution


  blue
• copper ions (Cu+): unstable in aqueous solution and disproportionate(redox)

  Quantitative analysis: Fe2+ (aq) + 2OH- (aq) ---> Fe(OH)2 (s)
• What is the colour produced? *colour is also produced if ammonia is used instead of sodium hydroxide*: green gelatinous preciptate

  Quantitative analysis: Fe3+ (aq) + 3OH- (aq) ---> Fe(OH)3 (s)
• What is the colour produced? *colour is also produced if ammonia is used instead of sodium hydroxide*: orange gelatinous precipitate

  Quantitative analysis: Cu2+ (aq) + 2OH- (aq) ---> Cu(OH)2 (s)
• What is the colour produced? *colour also produced if ammonia is used instead of sodium hydroxide*: pale blue gelatinous precipitate
• What happens when Cu(OH)2 (s) is added to excess Ammonia? redissolves upon addition of excess NH3 solution to give deep purple blue solution
• what does the colour of a transition metal depend on: the number of d electrons , arrangements of ligands around the ion , energies of the d orbital , number if each kind of ligand present
• how are coloured compounds made: ligands bind to the ions and split the 3d orbitals into 2 different energy levels
• where is the energy needed to cause electrons to move to excited states from: visible light
• amount of energy needed to jump depends on: central metal ion , oxidation state , ligands , coordination number
• what colour is the transition metal when there is a full 3d shell or empty 3d shell: white/colourless compound as no energy is absorbed so no electrons are excited
• complex ion/complex: central metal atom/ion surrounded by coordinately bonded ligands
• ligand: atom/ion/molecule (at least 1 lone pair) that donates a lone pair to the central transition metal ion to form a coordinate/dative covalent bond
• monodentate: ligand with only one lone pair and forms 1 coordinate/dative covalent bond
• bidentate: ligand with 2 lone pairs and forms 2 coordinate/dative covalent bonds
• polydentate: ligand with more than 2 lone pairs and forms more than 2 coordinate/dative covalent bonds
• Shapes of complexes: octahedral , tetrahedral , square planar , linear
• Shape of complex with a coordination number of 4: tetrahedral 109.5° or square planar 90° e.g [NiCl4]2- or [Ni(CN)4}2-
• Shape of complex with a coordination number of 2: linear e.g [Ag(NH3)2]+ 180°
• Shape of complex with a coordination number of 6: octohedral e.g [Fe(CN)6]3-

  As we know Cu+ ions are unstable in aqueous solutions and disproportionate.
• what is the equation for Cu+ ions which disproportionate into products? 2Cu+ (aq) ----> Cu2+ (aq) + Cu (s)

  
  

  or

  
  

  Cu2SO4 (s) + (aq) ---> Cu (s) + CuSO4 (aq)
• Why is it good that most transition metals compounds are coloured? Useful for quantitative analysis
• Does Fe(OH)2 (green ppt) dissolve in excess NH3?


  No