Transition metals

• Transition elements form coloured compounds when they gain or lose electrons.
• Copper(I) salts are red, copper(II) salts are blue
• Iron(II) salts are green, iron (III) salts are yellow/orange
• The colour is due to the absorption of light by unpaired d-electrons
• transition elements form compound in which that element has different oxidation states
• Transition elements form coloured compounds
• The elements and their compounds can act as catalysts
• Transition metal complexes are soluble in water
• Transition metal complexes are hard acids
• Transition elements for compound with more than one oxidation state
• properties that differ from other metals:

  • they form compounds in which the transition element has different oxidation states.
  • they form coloured compounds.
  • the elements and their compounds act as catalysts.
• number of oxidation states increases across the transition element series to manganese, and then decreases.
• potassium dichromate( VI) is bright orange
• cobalt (II) chloride is pink-purple
• nickel (II) sulphate is green, whilst hydrated nickel (II) sulphate is blue
• the solid compounds can be dissolved in water to create coloured solutions. The colour of the solution is linked to the partially filled d-orbitals of the transition metal ion. Colour of solution can vary with different oxidation states.
• chromium forms two common oxidation states, +3 and +6 in its compound.

  • Cr (III) - green
  • Cr (VI) - yellow or orange
• a catalyst is a substance that increases the rate of reaction without being used up itself. It works by providing an alternative reaction pathway with a lower activation energy
• transition metals and their compounds are important catalysts used in variety of industrial processes:

  • Haber process for the manufacture of ammonia from reaction between nitrogen and hydrogen. N2(g) + 3H2(g) = 2NH3(g)
  • Contact process in the production of sulphur trioxide from oxidation of sulphur dioxide. 2SO2(g) + O2(g) = 2SO3(g). The catalyst would be vanadium (V) oxide, V2O2(s).