Transition metals

• What is a transition metal

  an element with an incomplete d-subshell that can form at least one stable ion with an incomplete d-subshell
• Explain what is required for a substance to absorb visible light

  There must room for an electron in one orbital to be excited into another orbital, and the difference between their energy levels must correspond to a frequency of visible light.
• Which two elements in the d-block are exceptions to the Aufbau principle?

  Chromium [Ar] 4s1 3d5

  copper [Ar] 4s1 3d10
• Which two elements in the d-block are exceptions to the Aufbau principle?


  Chromium [Ar] 4s1 3d5

  copper [Ar] 4s1 3d10

  these configurations are energetically more stable.
• what are the general properties of transition metals?

  • Variable oxidation states
  • form complex ions
  • form coloured compounds
  • behave as catalysts
• Define coordinate bond (dative covalent)

  A covalent bond (shared pair of electrons) in which both the electrons came from the same atom
• Define ligand

  A molecule or ion that forms a coordinate bond with a transition metal ion by donating a pair of electrons
• Coordination number

  The number of dative covalent bonds
• complex ions always has a…

  metal ion at its centre and is surrounded by ligands. these can be:

  • ions
  • molecules
• the overall charge of a complex ions can be…

  positive

  negative

  or neutral
• what is the IUPAC name of this complex ion?

  Hexaaquacopper(II)

  
• What is the IUPAC name for this complex ion?

  Triaminetriaquacobalt(II)

  (name the ligand in alphabetical order when there are two neutral ligands)

  
• What metal ions are usually square planar ?

  Nickel

  palladium

  platinum
• ligands must have a lone pair of electrons to donate to the metal ion.

  give some examples that can act as ligands

  H2O - two lone pairs on the oxygen

  group 7 ions - 4 lone pairs

  NH3 - 1 lone pair on nitrogen

  amines - 1 lone pair on nitrogen

  carboxylate ions - 5 lone pairs across 2 oxygens
• Why does zinc not form a coloured compound

  Zinc has a full 3d orbital. Therefore there is no space for an electron to be excited to a higher energy level.

  There are no stable zinc ions with a partially filled 3D orbital.
• when is an atom in its ground state

  When all if its electrons are in their lowest possible energy Levels
• when is an atom in an excited state?

  when at least one of its electrons is not in its lowest possible energy level
• the energy difference between the non-degenerate d-obirtals correspond to varies frequency of visible light
• 
  

  the energy difference between the non-degenerate d-orbitals correspond to varies frequency of visible light
• how do you calculate the amount of energy absorbed by a compound ?

  the energy difference between the non-degenerate d-obirtals correspond to various frequency of visible light

  ΔE = h x v

  h = plack’s constant

  v= frequency (hertz)
• What are factors that affect the colour of a transition metal

  • type of ligand
  • the coordination number
  • oxidation state of transition metal ion
• show does the oxidation state of the transition metal ion affect the colour of a transition metal complex

  The higher the oxidation state means more d orbital splitting and so higher frequencies of light are absorbed.

  The stronger the interaction with the ligands The more d orbital splitting
• how does the type of ligand affect the colour

  Different ligands cause different degrees of d orbital splitting

  Cl- < H2O < NH3
• How does the coordination number affect the colour changes

  More ligands means more splitting of the d-orbital. Therefore complexes with higher coordination numbers absorb higher frequencies of light because of the greater degree of d-orbital splitting
• What two quantities is the absorbance proportional to

  Distance travelled by the beam through the solution

  the concentration of the sample
• why is calorimetry preferred over titrations

  a smaller volume of solution is used

  does not require the use of an indicator

  does not involve chemical change of the sample being analysed

  does not rely on personal judgement.
• Ligand substitution

  When one ligand in a complex is replaced by another
• incomplete substitution in copper(II) complexes with ammonia(NH3)

  state the equation

  state the colour change

  [Cu(H2O)6]2+ + 4NH3 —> [Cu(NH3)4(H2O)2]2+ + 4H2O

  light blue —> dark blue
• complete substitution without change in coordination number in cobalt(II) complexes

  state the equation

  state the colour change

  [Co(H2O)6]2+ + 6NH3 —> [Co(NH3)6]2+ + 6H2O

  pink solution to yellow solution
• change in co-ordination number in a copper (II) complex

  state the equation

  state the colour change

  [Cu(H2O)6]2+ + 4Cl- —> [CuCl4]2- + 6H2O

  blue to yellow
• define bidentate ligands These ligands are able to form ​two coordinate bonds​to the central metal ion as they have ​two.lone electron pairs​
• change in co-ordination number of a copper solution

  state the equation

  state the colour change

  [Cu(H2O)6]2+ +4Cl- —> [CuCl4]2- + 6H2O

  blue to yellow
• change in co-ordination number of cobalt solution

  [Co(H2O)6]2+ + 4Cl- —> [CoCl4]2- +6H2O

  pink to blue
• what is the chelate effect

  The replacement of monodentate ligands with bidentate and multidentate ligands in complex ions

  this is because entropy is likely to increase if there are more particles in the products than In the reactants.
• what do you get when EDTA reacts with Hexaaquacopper

  [Cu(H2O)6]2+ + EDTA4- —> [CUEDTA]2- + 6H2O
• EDTA

  EDTA can form 6 dative covalent bonds with a metal ion.

  And has a charge of 4-

  and can react quickly with any heavy metals in the body. Due to chelate effect.
• What are the two types of catalysts

  Heterogenous - different physical state (phase) from the reactants

  homogeneous - same physical state (phase) as the reactants
• give examples of a mondentate ligand

  NH3

  H2O

  Cl-
• give examples of bidentate ligands

  NH2CH2CH2NH2

  ethandioate ion
• give an example of a multidentate ligand

  EDTA4-