Transition Metals

• Transition metals are found in the centre of the periodic table and are known as d-block elements, which includes groups 3 to 12 of the periodic table.
• They exhibit properties unique to this set of elements: they are good conductors of heat and electricity, possess high densities and melting points, and are capable of forming coloured compounds.
• The variable oxidation states of transition metals stem from the fact that both the 4s and 3d electrons are available for bonding.
• Many transition metals exhibit catalytic properties due to their ability to adopt multiple oxidation states and to adsorb other substances on to their surface. Well-known examples include the use of iron in the Haber process and nickel in the conversion of alkene to alkane.
• Transition metals are able to form complex ions. These are central metal ions that are surrounded by ligands (usually small ions or molecules) which have lone pairs of electrons that can be donated into a d orbital on the central ion.
• Ligand substitution is a common reaction of transition metal complexes.
• Another significant property of transition metals is their ability to form stable partially filled d-orbitals. This stability can lead to unusual ion charges, such as Iron (II) and Iron (III).
• Transition metals and their compounds often exhibit paramagnetic behaviour as their atoms have unpaired d electrons.
• They can form compounds which are coloured, as their energy levels are split into 2 in the presence of ligands and can absorb certain wavelengths of light. The light not absorbed determines the colour observed.
• The enthalpy of atomisation of the transition metals is high as there are strong metallic bonds which are due to delocalised electrons above the metallic lattice.
• They often form alloys with other metals, which are mixtures of metallic elements that enhance the hardness and durability of the pure metal.
• They can demonstrate catalytic activity, due to the nature of empty or partially filled d-orbitals which can accept a wide variety of electron configurations and hence show varied activity.
• Industrial applications of transition metals include electroplating, catalysts in industry, generating coloured pigments in materials etc. Transition metals play an important role in biological systems as well, evidenced by the role of iron in haemoglobin.