GENERAL CHARACTERISTICS OF ACTINIDES

1. Oxidation states

The dominant oxidation state of these elements is +3 (similar to lanthanides). Besides +3 state, they also exhibit +4 oxidation state. Some actinides show still higher oxidation states. The maximum oxidation state first increases upto the middle of the series and then decreases i.e. it increases from +4 for Th to +5, +6 and +7 for Pa, V and Np but decreases in the succeeding elements.

2. Chemical behaviour

The ability of actinides to exist in different oxidation states has made their chemistry more complex. Moreover, most of these elements are radioactive and the study of their chemistry in the laboratory is difficult.

(a) They react with boiling water to give a mixture of oxide and hydride.

(b) The combine with most of the non – metals at moderate temperature.

(c) All these metals are attacked by HCl but the effect of HNO₃ is very small due to the formation of a protective oxide layer on their surface.