transition metals

Question 1

when ligands approach the central metal ion along a certain axis

how to decide energy levels of d orbitals

Answer 1

e.g. ligands approach central metal ion along z-axis
- highest energy orbital: electrons in orbital lying directly on the axis (i.e. dz2)
- lowest energy orbital: electrons in orbitals furthest from axis (i.e. dxy and dx2-y2)

Question 2

How carbon monoxide prevents oxygen from being transported around the body

Answer 2

• CO acts as a ligand and competes with oxygen to forms dative bonds to the central Fe2+ ion in haemoglobin
• CO is stronger ligand than O2 and hence binds irreversibly to haemoglobin
• thus this decreases its ability to carry oxygen to tissue around the body
• resultant oxygen deprivation causes death

Question 3

Suggestion of elements which are suitable as a (heterogenous) catalyst

Answer 3

• must be transition element
  -> have partially filled d orbitals which allow it to function as a heterogenous catalyst
• (if question asks you to suggest another element to act as a catalyst for a PARTICULAR reaction)
  element must have the same EC (i.e. from the same column)

Question 4

reasons for diff colours of transition metal compounds

Answer 4

• diff ligands
  
  • diff extent on splitting of d-orbitals
  • diff energy gap between split orbitals
  • lights of diff wavelength absorbed by electron
    => different complementary colour observed
• diff O.S. of central metal ion
  
  • diff EC of central metal ion
  • diff energy gap between split orbitals
  • lights of diff wavelength absorbed by electron
    => different complementary colour observed