What is "actinides"

Usage examples of "actinides".

This was Touch-Down Time, when the citizens of the bustling, prosperous planet of Fomalhaut V - rich in the transuranics, the actinides, so vital as the energy fuels needed to extend the surge of colonization to every habitable planet in the spiral of the Milky Way - relaxed industry and inhibitions in a three-day spectacular of day-long contests, night-long dancing, and eating and carousing.

And Ireta, a satellite of a suspected third generation sun, ought to be rich in the heavier elements, rich in the transuranics and actinides, neptunium, plutonium and the more esoteric of the rare elements above uranium on the periodic table, so urgently and constantly required by the Federation of Sentient Populations, the search for which was one of the primary tasks of the EEC.