Chemistry of Transition Series
The transition elements consist of three complete rows of ten elements and one incomplete row. These rows are called first, second and third transition series which involve the filling of 3d, 4d and 5d orbitals respectively. These series are also called transition series.
General Characteristics of Transition Elements:-
- Nearly all the transition elements have typical metallic properties such have high tensile strength, ductility, malleability, high thermal and electrical conductivity and metallic lustre.
- Except mercury which is liquid at room temperature, other transition elements have typical metallic structures.
- They have high melting and boiling points and have higher heats of vaporisation than non transition elements.
- The transition elements have very high densities as compared to metals of groups I and II (s- block).
- The first ionisation energies of d-block elements are higher than those of s-block elements but are lesser than those of p-block elements.
- They are electropositive in nature.
- Most of them form coloured compounds.
- They have good tendency to form complexes.
- They exhibit several oxidation states.
- Their compounds are generally paramagnetic in nature.
- They form alloys with other metals.
- They form interstitial compounds with elements such as hydrogen, boron, carbon, nitrogen, etc.
- Most of the transition metals such as Mn, Ni, Co, Cr, V, Pt etc. and their compounds have been used as good catalysts.