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84 chemistry reactive metals with low ionization enthalpies. valence (oxidation states), paramagnetism and They lose the outermost electron(s) readily to oftenly used as catalysts. However, Zn, Cd and form 1+ ion (in the case of alkali metals) or 2+ Hg which have the electronic configuration, ion (in the case of alkaline earth metals). The (n-1) d ns do not show most of the properties of transition elements. In a way, transition metallic character and the reactivity increase as we go down the group. Because of high metals form a bridge between the chemically reactivity they are never found pure in nature. active metals of s-block elements and the The compounds of the s-block elements, with less active elements of Groups 13 and 14 and thus take their familiar name “Transition the exception of those of lithium and beryllium are predominantly ionic. Elements”. 3.6.2 The p-Block Elements 3.6.4 The f-Block Elements (Inner-Transition Elements) The p-Block Elements comprise those belonging to Group 13 to 18 and these The two rows of elements at the bottom of the Periodic Table, called the Lanthanoids, together with the s-Block Elements are Ce(Z = 58) – Lu(Z = 71) and Actinoids, called the Representative Elements or Main Th(Z = 90) – Lr (Z = 103) are characterised by Group Elements. The outermost electronic 1-14 2 1 2 6 the outer electronic configuration (n-2)f configuration varies from ns np to ns np (n-1)d0–ns . The last electron added to each in each period. At the end of each period is element is filled in f- orbital. These two series a noble gas element with a closed valence of elements are hence called the Inner- 2 6 shell ns np configuration. All the orbitals Transition Elements (f-Block Elements). in the valence shell of the noble gases are They are all metals. Within each series, the completely filled by electrons and it is very properties of the elements are quite similar. difficult to alter this stable arrangement by The chemistry of the early actinoids is the addition or removal of electrons. The more complicated than the corresponding noble gases thus exhibit very low chemical lanthanoids, due to the large number of reactivity. Preceding the noble gas family oxidation states possible for these actinoid elements. Actinoid elements are radioactive. are two chemically important groups of non- Many of the actinoid elements have been made metals. They are the halogens (Group 17) and the chalcogens (Group 16). These two groups only in nanogram quantities or even less by nuclear reactions and their chemistry is not of elements have highly negative electron fully studied. The elements after uranium are gain enthalpies and readily add one or two called Transuranium Elements. electrons respectively to attain the stable noble gas configuration. The non-metallic Problem 3.3 character increases as we move from left to right across a period and metallic character Theelements Z=117and120havenotyet been discovered. In which family/group increases as we go down the group. would you place these elements and also give the electronic configuration in 3.6.3 The d-Block Elements (Transition each case. Elements) Solution These are the elements of Group 3 to 12 in the centre of the Periodic Table. These are We see from Fig. 3.2, that element characterised by the filling of inner d orbitals with Z = 117, would belong to the halogen family (Group 17) and the by electrons and are therefore referred to as d-Block Elements. These elements have el14tr10ic2co5figuration would be [Rn] the general outer electronic configuration 5f 6d 7s 7p . The element with Z = 120, 1-10 0-2 will be placed in Group 2 (alkaline earth (n-1)d ns except for Pd where its electronic metals), and will have the electronic configuration is 4d 5s . They are all metals. configuration [Uuo]8s . Theymostlyformcolouredions,exhibitvariable Reprint 2026-27