transition metals

• What are transition metals defined by?

  Elements in the d-block with partially filled d-orbital
• How do transition metals form positive ions?

  They lose electrons from the s-orbital first
• What are the common physical properties of transition metals?

  • Similar atomic radius
  • High densities
  • High melting points
  • High boiling points
• What are the special chemical properties of transition metals?

  • Form complexes
  • Form coloured ions
  • Variable oxidation states
  • Good catalysts
• What is a complex in chemistry?

  A central metal ion surrounded by ligands

  
• How can complexes be represented in formulas?

  Using square brackets
• What are ligands?

  Molecules or ions with a lone electron pair
• What are common ligands in transition metal complexes?

  • Cl^-
  • H₂O
  • NH₃
• What is the coordination number in a complex?

  Number of coordinate bonds around the metal ion
• What is the coordination number of silver complexes?

  2
• What is the coordination number of platinum complexes?

  4
• What happens during a ligand substitution reaction?

  Ligands are exchanged without changing coordination number
• Why can NH₃ and H₂O be exchanged in ligand substitution reactions?

  They are similar in size and uncharged
• What is the result of ligand substitution with NH₃ in excess?

  Incomplete substitution forms a combination of ligands
• What color does the complex ion form with NH₃ and copper?

  Deep blue solution
• What happens when Cl^- ligands substitute for NH₃ or H₂O?

  It results in a change in coordination number
• What is the coordination number of complexes with only Cl^- ligands?

  Four
• What shape do complexes with Cl^- ligands form?

  Tetrahedral shape
• What are bidentate ligands?

  • Form two coordinate bonds
  • Have two lone electron pairs
  • Examples: ethanedioate ions, ethane-1,2-diamine
• How do bidentate ligands affect coordination number?

  Coordination number remains at six
• What are multidentate ligands?

  • Form up to six coordinate bonds
  • Have multiple lone electron pairs
  • Example: EDTA
• What is the role of haem in the body?

  Transport oxygen around the body
• What is the effect of carbon monoxide on haem?

  It replaces oxygen in the haem complex
• What is the chelate effect?

  • Positive entropy change is favorable
  • More moles on the right than left
  • Substituting unidentate ligands with bidentate or multidentate ligands
• How does the free energy change (∆G) relate to entropy change?

  More negative ∆G means more favorable reaction
• What is the enthalpy change (∆H) for ligand substitution reactions?

  Very small, near zero
• What shape do octahedral complexes form?

  • Bond angle of 90°
  • Common with H₂O and NH₃ ligands
• What is cis-trans isomerism in octahedral complexes?

  • Ligands can be next to or opposite each other
  • Trans has same ligands opposite
  • Cis has same ligands next to each other

  
• What is optical isomerism in octahedral complexes?

  • Occurs with bidentate ligands
  • Isomers are mirror images of each other
• What shape do tetrahedral complexes form?

  • Bond angle of 109.5°
  • Formed with larger ligands like Cl^-
• What shape do square planar complexes form?

  • Consist of four coordinate bonds
  • Bond angle of 90°
  • Common with platinum and nickel
• What is the bond angle in linear complexes?

  180°
• What is the cis isomer of a square planar complex of platinum used for?

  Cancer therapy drug

  
• Why is only one isomer of cisplatin effective?

  Cells are chiral, only one fits
• What are the side effects of cisplatin?

  Hair loss and other serious effects
• What factors determine the color of transition metal ions?

  • Coordination number
  • Type of ligand
  • Oxidation state
• How does color arise in transition metal complexes?

  From absorbed and reflected light wavelengths
• What happens to electrons in the d-orbital when energy is applied?

  They move to a higher energy state
• What is the formula to calculate the change in energy (∆E)?

  ∆E corresponds to wavelength and frequency

  
• What is colorimetry used for?

  • Determine concentration of coloured ions
  • Uses absorption of visible light
  • Calibration graph for known concentrations