transition metals

• transition element


  d-block element which can form one or more stable ions with partially filled d subshell
• atomic radii


  TM atomic radii remain approximately constant

  across row…

  • no. proton increase, nuclear charge increase
  • as electrons are added to 3d subshell, the increase in no. inner 3d electrons provide more shielding btwn nucleus & outer 4s electrons, offsetting inctrase increase in nuclear charge
  • effective nuclear charge approx & thus efoa btwn nuclues and outer e- constant
• 1st IE


  approx constant

  across period, no. protons increase thus nuclear charge increases. however increasing number of electrons are being added to 3d subshell, increasing no. of inner 3d electroms provide more shielding effect on ve, offsetting increasing nuclear charge considerabl. as e- being rmved from 4s orbital, energy req to remove first e- is appeox constant
• complex


  contains a central metal atom OR ion linked to 1 or more surrounding ions, by dative cov bonds (if has overall charge, it is a complex ion)
• ligand


  ion or molecule which contains at least 1 atom bearing a lp of e- which can be donated into a low lying vacant orbital pf metal atom or ion, forming a dative cov bond
• large Kstab

  POE lies to the right, X more stable than Y, X stronger ligand than Y, X forms stronger dative cov bond with central metal atom/ion than Y, Y ligands readily replaced by X ligands
• large Enod value


  eg X readily reduced to Y, more stable
• mp

  higher than s block metals: valence 3d & 4s electrons are close in energy, oth available for delocalisation into sea of e-, with a greater no. of delo e- & higher cd of cations, metallic bonding stronger in TM
• density: denser than s-block metals

  TM have smaller atomic radius -> greater no. atoms per unit vol

  larger atomic mass -> greater mass per unit volume
• variable OS

  3d & 4s electrons close in energy, both available for bond formation
• lower OS : ionic

  higher OS : covalent
• highest possible OS

  no. unpaired d-electrons + 4s electrons
• why can TM act as HETERO catalyst

  availability of a partially filled 3d subshell allows for ready exchange of e-, to and from rxtant mols, facilitating fmtn of weak bonds w rxtant mols
• why can TM act as homo catalyst

  • ability to exist in diff OS
  • ease of converting from one OS to another
  • facilitating fmtn & decomp of intermediate formed from rx. of TM catalyst & reactants
• coordination no.


  total no. of dative cov bonds that central metal atom / ion formed w ligands
• conditions for complex formation

  • presence of ligands to donate e- pair to form dative cov bonds
  • presence if central metal atom / ion to (i) attract lp e- from ligand (ii) low-lying vacant orbitals to accommodating lp e- to form a dative cov bond
• why TM high tendency for complex fmtn

  • low-lying vacant orbitals
  • HIGH CD: relatively small ion & high charged, able to attract lp e- from ligands, high pp producing strong tendency towards cov bonding w ligands
• why is aq fecl3 acidic

  high charge small atomic rad, high cd, high pp, distorts e- cloud of h2o mols bonded to it, weakening O-H bonds, enabling H2O mols bonded to it to become proton donors, free H2O mols in soln act as bases (free h2o -> h3o+)
• splitting 3d orbitals

  • presence of ligands cause splitting of 5 3d orbitals in TM into 2 sets pt diff E lvls
  • since 3d SUBSHELL is partially filled
  • e- from lower-energy d orb can absorb E corresponding to certain WL from visible colour spectrum, promoted to higher-energy d orbital
  • colour obs is compliment of colour abs
• factors affecting energy gap (& thus colour) of complex

  type of metal & its OS (no. of d electrojs present)

  • diff no. d e-, repel e- of ligands to a diff extent, diff E gap

  type of ligand

  • diff ligand, at diff extents, split d orbitals of metal ion into 2 sets of slightly diff E lvls, thus e- from lower energy d orbital will absorb E corresponding to diff WL from visible colour spectrum, diff colour abs, diff colour obs
• Cu precipitation (usually NH3, NaOH)

  NH3: blue -> light blue ppt -> dark blue

  NaOH: blue -> light blue ppt

  ppt is Cu(OH)2

  conc HCL: yellow green
• Fe

  [Fe(H2O)]3+: yellow/ lilac

  [Fe(H2O)]2+: light green

  [Fe(SCN)(H2O)5]2+: blood red

  [Fe(C2O4)]3-: clc
• Co

  [Co(H2O)6]2+: pink
• Ni


  green

  ppt: light green

  Ni(NH3)6+: blue

  conc hcl: (NiCl4)2- blue
• V

  • most stable V4+
  • V(H2O)2+ unstable since it is oxidised by O2
• Cr (increasingly alkaline)


  green / violet (3+)

  blue (2+)

  (CrO4)2-: yellow

  (Cr2O7)2-: orange
• Mn

  pale pink

  MnO2: brown

  (MnO4)-: deep purple
• Ag

  ligand strength:

  edta > S > CN > I > S2O3 > Br > NH3 > Cl > H2O

  clc > black PPT > clc > yellow PPT > clc > cream PPT > clc > white ppt > clc