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 ligands in transition metal complexes?

  • 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 a change in 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 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 do bidentate ligands affect coordination number?

  They replace two unidentate ligands but keep the coordination number at six
• What are multidentate ligands?

  • Ligands that can form up to six coordinate bonds
  • Have multiple lone electron pairs
  • Common example: EDTA
• 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 in the haem complex
• 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 shape of silver complexes?

  Linear
• What is the bond angle in linear complexes?

  180°
• What is cisplatin 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 factors determine the color of transition metal ions?

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

  • Due to absorption and reflection of light
  • Some wavelengths are absorbed, others are reflected
  • The reflected wavelengths correspond to a specific color
• What happens to electrons in the d-orbital when energy is applied?

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

  ∆E = hν

  
• What is Planck's constant?

  1. 63 x 10^-34
• What is colorimetry?

  • An analytical technique
  • Uses absorption to determine concentration
• What factors determine the color of transition metal complexes?

  The coordination number, type of ligand, and oxidation state
• How does color arise in substances?

  Color arises from how substances absorb and reflect light