Example 4.10

Example . . Actinoid contraction is greater from element to element than lanthanoid contraction. Why? are restricted to collection items and the contemporary UK ‘copper’ coins are copper-coated steel. The ‘silver’ UK coins are a Cu/Ni alloy. Many of the metals and/or their compounds are essential catalysts in the chemical industry. V O catalyses the oxidation of SO in the manufacture of sulphuric acid. TiCl with A1(CH ) forms the basis of the Ziegler catalysts used to manufacture polyethylene (polythene). Iron catalysts are used in the Haber process for the production of ammonia from N /H mixtures. Nickel catalysts enable the hydrogenation of fats to proceed. In the Wacker process the oxidation of ethyne to ethanal is catalysed by PdCl . Nickel complexes are useful in the polymerisation of alkynes and other organic compounds such as benzene. The photographic industry relies on the special light-sensitive properties of AgBr. The d -block consisting of Groups - occupies the large middle section of the periodic table . In these elements the inner d orbitals are progressively filled. The f -block is placed outside at the bottom of the periodic table and in the elements of this block, f and f orbitals are progressively filled. Corresponding to the filling of d , d and d orbitals, three series of transition elements are well recognised. All the transition elements exhibit typical metallic properties such as –high tensile strength, ductility, malleability, thermal and electrical conductivity and metallic character. Their melting and boiling points are high which are attributed to the involvement of ( n – ) d electrons resulting into strong interatomic bonding . In many of these properties, the maxima occur at about the middle of each series which indicates that one unpaired electron per d orbital is particularly a favourable configuration for strong interatomic interaction. Successive ionisation enthalpies do not increase as steeply as in the main group elements with increasing atomic number. Hence, the loss of variable number of electrons from ( n – ) d orbitals is not