transition metals

• What are transition metals defined as in the periodic table?


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


  By losing 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?


  • They form complexes
  • They form coloured ions
  • They have variable oxidation states
  • They act as good catalysts
• What is a complex in the context of transition metals?


  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 that form coordinate bonds
• What are common examples of ligands?


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


  The number of coordinate bonds formed around the central 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 the coordination number
• Why can NH₃ and H₂O ligands be exchanged without changing coordination number?


  They are similar in size and both uncharged
• What is the result of ligand substitution with Cl^- ligands?


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


  4
• What shape do complexes with Cl^- ligands form?


  Tetrahedral shape
• What are bidentate ligands?


  • Ligands that can form two coordinate bonds
  • Have two lone electron pairs
  • Examples include ethanedioate ions and ethane-1,2-diamine
• How does the coordination number change when bidentate ligands replace unidentate ligands?


  The coordination number remains at six
• What are multidentate ligands?


  • Ligands that can form multiple coordinate bonds
  • Can form up to six coordinate bonds
  • Example: EDTA (ethylenediaminetetraacetic acid)
• What is the role of haem in the body?


  It transports oxygen around the body
• What is the effect of carbon monoxide on haemoglobin?


  It replaces oxygen, preventing transport
• What is the chelate effect in ligand substitution reactions?


  • A positive entropy change is favorable
  • More moles on the right than the left is preferred
  • Achieved by substituting unidentate ligands with bidentate or multidentate ligands
• How does the enthalpy change (∆H) for ligand substitution reactions typically behave?


  It is very small, near zero
• What shape do octahedral complexes typically have?


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


  • Occurs with different types of unidentate ligands
  • Cis has same ligands next to each other
  • Trans has same ligands opposite each other
• What is optical isomerism in octahedral complexes?


  • Shown by complexes with bidentate ligands
  • Two isomers are mirror images of each other
• What shape do tetrahedral complexes have?


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


  • Formed by platinum and nickel complexes
  • Consists of four coordinate bonds with a bond angle of 90°
• What is the bond angle in linear complexes?


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


  As a cancer therapy drug
• Why is only one isomer of cisplatin effective in treating cancer?


  Only one isomer fits the chiral cells
• What are the side effects of cisplatin?


  It can cause hair loss
• What determines the colour of transition metal ions?


  Coordination number, type of ligand, and oxidation state
• How does colour arise in transition metal complexes?


  Due to absorption and reflection of light wavelengths
• What happens to electrons in the d-orbital when energy is applied?


  They move from ground state to excited state
• What is the formula to calculate the change in energy (∆E) between energy states?


  ∆E corresponds to a wavelength and frequency of light
• What is colorimetry used for?


  • An analytical technique
  • Uses absorption of visible light
  • Determines concentration of coloured ions
• How is a calibration graph used in colorimetry?


  It is produced by measuring known concentrations to calibrate the colorimeter
• What is a key property of transition metals regarding oxidation states?


  They have variable oxidation states
• What oxidation states does vanadium have?


  From +5 to +2