<chemical>

Einsteinium. A man-made radioactive actinide with atomic symbol es, atomic number 99, and atomic weight 252. Its known isotopes range in mass number from 243-246. Its valence can be +2 or +3. Einsteinium was originally discovered in the debris from a thermonuclear explosion in 1952.

Chemical name: Einsteinium

(12 Dec 1998)