d- and f-Block Elements
d- and f-Block Elements focuses on electronic configurations, variable oxidation states, colour, magnetism and lanthanide contraction. Learn to read a configuration and predict behaviour.
Configurations and properties
d-block atoms fill (n-1)d and ns orbitals. Cr is [Ar]3d5 4s1 and Cu is [Ar]3d10 4s1 because half-filled and fully filled sets are stable. Transition metals show variable oxidation states, catalysis, colour and paramagnetism. Colour arises from d-d transitions; Sc3+, Ti4+ and Zn2+ are colourless because their d subshells are empty or full. Spin-only magnetic moment is mu = sqrt(n(n+2)) BM, where n is unpaired electrons.
Lanthanides and manganese
Lanthanides commonly show +3; Ce4+ and Eu2+ are important exceptions. Lanthanide contraction is the steady decrease in size across the series and makes Zr and Hf similar. KMnO4 is reduced to Mn2+ in acid, MnO2 in neutral or weakly alkaline medium, and MnO4^2- in strong alkali.
Worked example
Fe3+ is d5. In a high-spin octahedral field it has five unpaired electrons, so mu = sqrt(5 x 7) = sqrt(35) = 5.92 BM. The reasoning is to count unpaired d electrons, not total electrons. A low-spin d5 case would have one unpaired electron and a much smaller moment.
Traps
Filling 4s after 3d when writing ions (4s electrons are removed first), treating Zn as a typical transition metal, and forgetting that colour needs partially filled d orbitals are common mistakes.