2.5 Transition metals

Introduction Transition Metals A2 ChemistryThe 3d block contains 10 elements, all of which are metals.

Unlike the metals in Groups 1 and 2, the transition metals Ti to Cu form coloured compounds and compounds where the transition metal exists in different oxidation states.

Some of these metals are familiar as catalysts (from kinetics and transition metals).

Transition metal characteristics of elements Ti–Cu arise from an incomplete (or partially filled) d orbitals in atoms or ions.

The characteristic properties include:
complex formation
formation of coloured ions
variable oxidation states
catalytic activity


Iron and copper chemistry - Iron and copper were first encountered during AS Chemistry’s ‘Extraction of Metals‘ topic. The link between both metals being exemplified by the use of scrap iron to extract copper from copper (II) ions: Fe(s) + Cu2+(aq) → Cu(s) + Fe2+(aq) (blue)                        (green) This method of copper extraction, usually from low-grade
Chromium, cobalt, vanadium and manganese chemistry - At lower oxidation states, transition metals form ionic bonds e.g. Mn2+ and Cr3+  At higher oxidation states, transition metals cannot form monatomic ions. Instead they bond covalently with electronegative elements (like oxygen) to form compounds or molecular ions e.g. oxoanions such as MnO4−and Cr2O72-. In general,  Reduction, from high to low metal oxidation state, is more feasible in acidic transition
Catalysts (transition metals) - Mechanism of catalysis The minimum energy required for reactants to undergo a chemical reaction is known as the Activation Energy (Ea). A catalysed reaction provides an alternative route for the chemical reaction at a lower activation energy, hence increases the rate of reaction. Transition metals, by virtue of their ability to readily change their oxidation states, generate intermediate species that enable the
Variable oxidation states (transition metals) - Transition elements show variable oxidation states, as electrons may be lost from energetically similar 4s and 3d sub-levels. Terminology: the oxidation state of the metal in a compound is indicated by a Roman numeral after the name of the metal. So Iron (II) means a compound containing Fe2+ .  Oxidation states of chromium Species Colour Oxidation state of metal K2CrO4
Formation of coloured ions - Transition metal ions can be identified by their colour Why transition metals form coloured complexes? 1. Complexes shows different energy levels for its d electrons due to d orbital splitting. Metal ions, with incompletely filled d sub-orbitals, experience energetic splitting of their five d sub-orbitals upon binding with ligands. Two groups of d sub-orbitals are formed: one group will be
Complex formation and substitution reactions involving transition metals - Definitions A ligand is a molecule or ion that forms a co-ordinate bond (dative covalent) with a transition metal by donating a pair of electrons to the central transition metal ion. The lone pair on the ligand is donated into the partially filled d sub-level of the transition metal. All ligands are lone pair donors. In other words, all ligands function as
General properties of transition metals - Transition metal characteristics of elements Ti–Cu arise from an incomplete d orbitals in atoms or ions. The characteristic properties include: • complex formation • formation of coloured ions • variable oxidation states • catalytic activity. Definitions A d-block element has its highest energy electron in its d sub-level A transition element is a d-block element that can form one or more stable

 

OCR Transition metals sample chapter (click here for pdf)