Developing Metals - Topic 9

• transition metal


  an element which forms at least one ion with a partially filled electron subshell

  
• physical properties of transition metals

  high melting and boiling points , high densities , slightly low atomic radius
• Why isn't scandium a transition metal?

  SR3+ ion loses 3e to then have an empty d subshell
• Why isn't zinc a transition metal?

  ZN2+ loses 2e to then have a full d subshell
• what is lost first the s electrons or d electrons


  s electrons
• chemical properties of transition metals

  variable oxidation states , coloured ions in solution
• what is special about chromium

  one electron in each d orbital and 1 electron in 4s subshell to increase stability
• what is special about copper

  prefers one full 3d subshell and one electron in 4s
• 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 atoms on metal surface to form weak bonds known as chemisorption
• homogenous catalysis


  transition metal catalyses reaction in its aqueous phase as an ion , the transition metal then forms an intermediate compound which breaks down to form products

  
• catalytic action of cobalt

  reactant - contains CO2+ (pink)

  intermediate - contains CO3+ (green)

  product- contains CO2+ (pink)
• Fe2+ colour in aqueous solution


  green
• Fe3+


  orange/brown
• Cu+


  unstable in aqueous solution
• Cu2+


  blue
• copper ions


  unstable in aqueous solution and disproportionate(redox)
• Fe(OH)2


  green gelatinous preciptate
• Fe(OH)3


  orange gelatinous precipitate
• Cu(OH)2


  pale blue gelatinous precipitate
• Cu(OH)2


  redissolves upon addition of excess NH3 solutio to give deep purple blue solution

  only OH- source from NH3 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 that donates a lone pair to the central transition metal ion to form a coordinate bond
• monodentate


  ligand with only one pair and forms 1 coordinate bond
• bidentate


  ligand with 2 lone pairs and forms 2 coordinate bonds
• polydentate


  ligand with more than 2 lone pairs and forms more than 2 coordinate bonds
• shapes of complexes


  octahedral , tetrahedral , square planar , linear

  
• coordination number 4


  tetrahedral 109.5° or square planar 90° e.g [NiCl4]2- or [Ni(CN)4}2-

  
• coordination number 2


  linear e.g [Ag(NH3)2]+ 180°

  
• coordination number 6


  octohedral e.g [Fe(CN)6]3-