energetically unfavourable. The involvement of ( n – ) d electrons in the behaviour of transition elements impart certain distinct characteristics to these elements. Thus, in addition to variable oxidation states, they exhibit paramagnetic behaviour, catalytic properties and tendency for the formation of coloured ions, interstitial compounds and complexes. The transition elements vary widely in their chemical behaviour.
Many of them are sufficiently electropositive to dissolve in mineral acids, although a few are ‘noble’. Of the first series, with the exception of copper, all the metals are relatively reactive. The transition metals react with a number of non-metals like oxygen, nitrogen, sulphur and halogens to form binary compounds. The first series transition metal oxides are generally formed from the reaction of metals with oxygen at high temperatures.
These oxides dissolve in acids and bases to form oxometallic salts. Potassium dichromate and potassium permanganate are common examples. Potassium dichromate is prepared from the chromite ore by fusion with alkali in presence of air and acidifying the extract. Pyrolusite ore (MnO ) is used for the preparation of potassium permanganate.
Both the dichromate and the permanganate ions are strong oxidising agents. The two series of inner transition elements , lanthanoids and actinoids constitute the f -block of the periodic table. With the successive filling of the inner orbitals, f , there is a gradual decrease in the atomic and ionic sizes of these metals along the series ( lanthanoid contraction ). This has far reaching consequences in the chemistry of the elements succeeding them.
Lanthanum and all the lanthanoids are rather soft white metals. They react easily with water to give solutions giving + ions. The principal oxidation state is + , although + and + oxidation states are also exhibited by some