For example, they exhibit variable oxidation states, form coloured complexes with different anions and neutral molecules and show paramagnetic behaviour. (iii) Enthalpy of atomization is the amount of heat required to break the metal lattice to get free atoms. The question is the catalytic properties of d block elements and the uses of d block element catalyst The following generalizations can be obtained from the ionisation energy values given above. d- Block Elements Short Answer Questions: **1. Introduction to General Properties of the Transition Elements. Transition Elements. Catalytic property of d and f Block Elements : A catalyst is a substance that alters the rate of a reaction by directing the reaction in an alternative pathway that requires lower activation energy. (i) The ionisation energies of these elements are high, and in the most cases lie between those of s- and d-block elements. Formation of coloured ions 4 Catalytic Properties 5 Variable oxidation states 6 Magnetic Properties 7 Complex formation 8 Formation of alloys 1 Atomic and Ionic Radii The atomic and ionic radii of transition elements are smaller than those of p- block elements and larger than those of s-block elements. In d-block, oxidation states differ by one, whereas in p-block… Elements having electrons (1 to 10) present in the d-orbital of the penultimate energy level and in the outer most ‘s’ orbital (1-2) are d block elements. * in kJ mol-1. Electrons in the outer shells of the atoms of these elements have little shielding effects resulting in an increase in effective nuclear charge due to the addition of protons in the nucleus. 7.Melting and Boiling points: – All transition elements have high melting and boiling point because of strong metallic bond between atoms of metals. Transition metals and their compounds also possess catalytic properties. This indicates that the transition elements are less electropositive than s-block elements. Hence, they possess similar chemical properties. Explain Werner’s theory of coordination compounds with suitable examples A: The important postulates of Werner’s theory are: i) In coordination compounds the metal atom exhibit two types of valency a) Primary valency b) secondary valency The partially filled subshells of d-block elements incorporate (n-1) d subshell.All the d-block elements carry a similar number of electrons in their furthest shell. In p-block, lower oxidation state is more stable due to inert pair effect, whereas in ehblock elements higher oxidation states are more stable. i) Due to variable oxidation states of transition metals they can absorb and re-emit a wide range of energies. Although electrons do not fill up ‘d’ orbital in the group 12 metals, their chemistry is similar in many ways to that of the preceding groups, and so considered as d block elements. The elements with incompletely filled d-subshell in their ground state or most stable oxidation state are named as D-block elements.They are additionally named as transition elements.The partially filled subshells incorporate the (n-1) d subshell.All the d-block elements have a similar number of electrons in the furthest shell. It is due to similar energy of (n – 1 )d and ns orbitals, electrons from both can be lost. Transition elements are those elements that have partially or incompletely filled d orbital in their ground state or the most stable oxidation state. Osmium has highest density because atomic volume of d-block elements are low and electron enter into (n-1)d sub-shell. (ii) d-block elements exhibit more oxidation states due to small energy gap between ns and (n – 1)d subshell while f – block elements show less oxidation state due to large energy gap between ns and (n -2)f subshell. Thus, they can provide necessary activation energy. 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