The Actinoids are in the range of – . to – . V except for Eu for which the value is – . V.
This is, of course, a small variation. The metals combine with hydrogen when gently heated in the gas. The carbides, Ln C, Ln C and LnC are formed when the metals are heated with carbon. They liberate hydrogen from dilute acids and burn in halogens to form halides.
They form oxides M O and hydroxides M(OH) . The hydroxides are definite compounds, not just hydrated oxides. They are basic like alkaline earth metal oxides and hydroxides. Their general reactions are depicted in Fig.
. . The best single use of the lanthanoids is for the production of alloy steels for plates and pipes. A well known alloy is mischmetall which consists of a lanthanoid metal (~ %) and iron (~ %) and traces of S, C, Ca and Al.
A good deal of mischmetall is used in Mg-based alloy to produce bullets, shell and lighter flint. Mixed oxides of lanthanoids are employed as catalysts in petroleum cracking. Some individual Ln oxides are used as phosphors in television screens and similar fluorescing surfaces. The actinoids include the fourteen elements from Th to Lr.
The names, symbols and some properties of these elements are given in Table . . Table . : Some Properties of Actinium and Actinoids Electronic conifigurations* Radii/pm Atomic Name Symbol + + Number Actinium Ac d s Thorium Th d s Protactinium Pa d s Uranium U d s Neptunium Np d s Plutonium Pu s Americium Am s Curium Cm d s Berkelium Bk s Californium Cf s Einstenium Es s Fermium Fm s