13.2 Coloured complexes

Question 1

Colours of transition metals

Answer 1

Sc³⁺ and Zn²⁺ colourless

Question 2

Why do transition metals appear coloured?

Answer 2

Their ions absorb opposite colours - absorb light because d orbitals are splint into two sub-levels - 3d e are excited from the lower to higher e levels - come back release a photon of coloured light

Question 3

Which factors influence the colour of the transition metal complex?

Answer 3

• nuclear charge and identitiy of the cnetral ion
• charge density of the ligand
• geometry of the complex ion
• number of e present - ox number of central ion

Question 4

Why same configuration can produce different colours?

Answer 4

Question 5

Why different colours are produced by [Cu(H₂O)₆]²⁺ and [Cu(NH₃)₄(H₂O)₂]²⁺?

Answer 5

Because ammonia has greater charge density than water - produces large split in d orbitals

Question 6

Function of spectrochemical series

Answer 6

Arrange ligands according to E separation between two sets of d orbitals

I^- lowest charge density - repels d e - smallest splitting

Cl^- - high density charge - larger splitting

Largest splitting oc CN^- and CO due to pi bonds - pi e interact with d orbitals