number of unpaired electrons increases from Sc to Cr and then decreases.
g. Catalytic properties: Most of transition metals are used as catalyst because of( i) presence of incomplete or empty d – orbitals,( ii) large surface area,( iii) varuable oxidation state,( iv) ability to form complexes, e. g., Fe, Ni, V 2 O 3, Pt, Mo, Co and used as catalyst.
h. Formation of coloured compounds: They form coloured ions due to presence of incompletely filled d – orbitals and unpaired electrons, they can undergo d – d transition by absorbing colour from visible region and radiating complementary colour.
i. Formation of complexes: Transition metals form complexes due to( i) presence of vacant d – orbitals of suitable energy( ii) smaller size( iii) higher charge on cations.
j. Interstitial compounds: Transition metals have voids or interstitials in which C, H, N, B etc. can fit into resulting in formation of interstitial compounds. They are non – stoichiometric, i. e., their composition is not fixed, e. g., steel. They are harder and less malleable and ductile.
k. Alloys formation: They form alloys due to similar ionic size. Metals can replace each other in crystal lattice, e. g., brass, bronze, steel etc.