Describe the general characteristics of the transition elements with special reference to their tendency to:
(i) Exhibit paramagnetism.
(ii) Form complex compounds.
(iii) Their catalytic behaviour.
(i)
Transition elements show paramagnetism. Paramagnetism is due to the presence of unpaired electrons in the d-orbitals of transition metal atoms, ions or molecules. The greater the number of unpaired electrons, the greater is the paramagnetism.
(ii)
Transition elements have strong tendency to form complex ion. This is because transition elements form small, highly charged ions, which have vacant (n – 1) d-orbitals of approximately the appropriate energy to accept lone pairs of electrons donated by other groups or molecules, such as cyanide ion, water and ammonia molecules.
(iii)
Most of the transition elements act as catalyst e.g., finely divided nickel is used in the hydrogenation of vegetable oils, iron in the manufacture of ammonia by Haber’s Process. This is because transition elements form transient intermediate complexes utilising empty d-orbitals. Consequently, low energy path-ways for slow reactions are provided which increase the rate of the reaction.
How is the variability in the oxidation states of transition metals different from that of the nontransition metals? Illustrate with examples.
Assign reasons for the following:
The enthalpies of atomisation of transition metals are high.
In what way are the observed oxidation states of the lanthanides related to their electronic configurations?
