Transition Elements

1. Transition elements are d block elements that have an ion with an incomplete d subshell. Transition Elements Zinc and Scandium are not transition elements! Scandium forms only one ion, Sc3+. In forming this ion, scandium loses the two electrons in the 4s subshell and the one electron in the 3d subshell. This leaves the ion with no d subshell – it therefore isn’t a transition metal. Zinc forms only one ion, Zn2+. In forming this ion, zinc loses the two electrons in the 4s subshell. This leaves the ion with a complete d subshell – it therefore isn’t a transition metal. Note that chromium and copper don’t fit the pattern. They fill their 3d subshell before their 4s subshell.

2. Transition Metals have variable Oxidation States Cr2O72- + 6H+ + 6e- 2Cr3+ + 7H2O MnO4- + 8H+ + 5e- Mn2+ + 4H2O Orange Green Purple Pale Pink Fe3+ + e- Fe2+ Pale green  Yellow Precipitation reactions of Transition Metals Catalytic Activity • Iron in the Haber Process:combines hydrogen and nitrogen to make ammonia • Nickel in the hydrogenation of C=C bonds: manufacture of margarine from vegetable oils. • Vanadium(V) oxide in the Contact Process: reaction which converts sulphur dioxide into sulphur trioxide. Sulphur dioxide gas is passed together with air (as a source of oxygen) over a solid vanadium(V) oxide catalyst. • Manganese (IV) Oxide in the decomposition of hydrogen peroxide N2 + 3H2 2NH3 CH2= CH2 + H2CH3CH3 3. 2SO2 + O2  2SO3 4. H2O2 H2O + ½ O2