transition metals

• what is the electron configuration of argon, used in the shorthand of the transition metals

  $1s^22s^22p^63s^23p^6$
• what is a transition metal

  a metal that can form one or more stable ions with an incomplete d sub-shell
• what are the 2 d block elements that arent transition metals

  Sc and Zn as they do not form a stable ion with an incomplete d sub-shell
• what are the 4 characteristic properties of transition metals

  • variable oxidation states
  • form coloured ions and compounds
  • catalytic activity
  • form complexes
• what is a complex

  a central metal ion surrounded by ligands
• what is a ligand

  a molecule or ion that forms a co-ordinate bond with a transition metal by donating a pair of electrons
• what is a monodentate ligand

  a molecule or ion that donates one electron pair to the central metal ion to form one co-ordinate bond
• what are the monodentate ligands

  • water
  • ammonia
  • chloride ion
  • cyanide ion
• what is a bidentate ligand

  a molecule or ion that has two atoms that each donate an electron pair to the central metal ion to form two co-ordinate bonds
• what are the bidentate ligands

  1,2-diaminoethane (H2NCH2CH2NH2)

  ethanedioate ion (C2O4 2-)
• what is a multidentate ligand

  a molecule or ion that has more than two atoms that each donate an electron pair to the central metal ion to form more than two co-ordinate bonds
• what is a co-ordination number

  the number of co-ordinate bonds to the central metal atom or ion
• what is the shape of a complex with 6 co-ordinate bonds

  octahedral, bond angle of 90
• whats the shape of a complex with 4 co-ordinate bonds

  tetrahedral, bond angle of 109.5 or square planar, bond angle of 90
• whats the shape of a complex with 2 co-ordinate bonds

  linear, bond angle of 180
• what is a lignad substitution reaction

  when one ligand is replaced by another
• what is haem

  an iron (II) complex with a multidentate ligand
• what is the chelate effect

  when a monodentate ligand is replaced by bidentate or multidentate ligands there is an increase in entropy. the reaction is always feasible as $\Delta G<0$. so the new complex formed will be more stable
• define stereoisomers

  compounds with the same structural formula but a different arrangement of atoms in space
• which complexes can exhibit stereoisomers

  square planar and octahedral
• what kind of stereoisomerism do square panar complexes exhibit

  cis-trans isomerism
• what is trans isomerism

  when each ligand is on the opposite side of the central metal ion/atom
• when can cis-trans isomerism occur

  when a square planar complex as two different ligands
• what is cis isomerism

  when each ligand pair is on the same side of the central metal atom
• can octahedral complexes exhibit cis-trans isomerism

  yes
• when can octaherdal complexes exhibit cis-trans isomerism

  when there are 2 different ligands, 2 of one and 4 of another
• what other kind of isomers can octahedral complexes form

  optical isomers
• what is optical isomerism

  non-superimposable mirror images
• when does optical isomerism occur in octahedral complexes

  when they contain bidentate ligands
• Oxidation state and colour of VO2+

  +5 and yellow
• Oxidation state and colour of VO2+

  +4 and blue
• oxidation state and colour of V3+

  3+ and green
• oxidation state and colour of V2+

  2+ and lilac
• what is the redox potential of an ion or atom

  a measure of how easily it is reduced to a lower oxidation state. the more positive the redox potential the more likely the ion to be reduced, so the less stable the ion will be
• what are the ligands surrounding the central metal ion in a standard electrode potential

  water
• what is a catalyst

  a substance that increases the rate of a chemical reaction without being changed in chemical composition or amount, and provides an alternate reaction route with a lower activation energy
• what is a heterogeneous catalyst

  a catalyst in a different state to the reactants
• how does a heterogeneous catalyst work

  adsorption- reactant molecules stick to the surface of catalyst

  chemical reaction- bonds in reactants are weakened and reaction occurs

  desorption- products leave surface, catalyst is regenerated
• what is catalyst poisoning

  impurities in the reactants may bind to the active sites blocking the reactants, which reduces the efficiency of the catalyst because reactants can’t bind to the surface
• what are homogeneous catalysts

  catalysts in the same state as the reactants