Element number 89 is actinium. The element, discovered by Friedrich Oskar Giesel in 1902, is a silvery white radioactive metal. The word actinium comes from the Greek word ‘aktis’ or ‘aktinos’, which means beam or ray. It is so radioactive that it glows in the dark. The element’s radioactivity, its rarity and hence its high cost have made actinium the least industrially useful element. Actinium is represented as Ac.
Element number 90, thorium is named after Thor, the Nordic god of thunder, lightning and storm. A highly radioactive element, thorium is a silvery, lustrous metal. It is potentially an alternative to uranium in fuelling nuclear reactors. In its liquid state, thorium has a greater temperature range than any is other element, with nearly 3,000 degrees Celsius. Since thorium is a health hazard, its use has steadily come down over the years. It is represented as Th.
Protactinium is a bright silvery metal. The element with the atomic number 91 decays to form another metal actinium. The name protactinium means before actinium. Discovery of the element is attributed to Otto Hahn and Lise Meitner. The element was isolated by Aristid von Grosse. It has no known uses.
Protactinium’s atomic symbol is Pa.
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