13.2 - The 'd' block elements

13.2.1 - List the characteristic properties of transition elements. Restrict this to variable oxidation states, complex ion formation, coloured compounds and catalytic properties.

13.2.2 - Identify which elements are considered to be typical of the d-block elements. Sc and Zn are not typical.

13.2.3 - Describe the existence of variable oxidation states in d-block elements. The 4s and 3d sub-levels are close in energy. Students should know that all d-block elements can show an oxidation state of +2. In addition, they should be familiar with the oxidation states of the following: Cr (+3, +6), Mn (+4, +7), Fe (+3) and Cu (+1).

13.2.4 - Define the term ligand.

13.2.5 - Describe how complexes of d-block elements are formed. Suitable examples are: [Fe(H2O)₆]³⁺, [Fe(CN)₆]^3-, [CuCl₄]^2-, [Cu(NH3)₄]²⁺, [Ag(NH₃)₂]⁺. Only monodentate ligands are required.

13.2.6 - Explain why some complexes of d-block elements are coloured. Students need only know that in complexes the d orbitals are split into two sets at different energy levels and the electronic transitions that take place between them are responsible for their colours.

13.2.7 - Outline the catalytic behaviour of d-block elements and their compounds. Limit this to:
MnO2 in the decomposition of hydrogen peroxide
V2O5 in the Contact process
Fe in the Haber process
Ni in the conversion of alkenes to alkanes. The mechanisms of action are not required.

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