An Etymological Dictionary of Astronomy and Astrophysics

A radioactive metallic → transuranium element belonging to the → actinides; symbol Es. → Atomic number 99, → mass number of most stable
→ isotope 254 (→ half-life 270 days). Eleven isotopes are known. The element was first identified by A. Ghiorso and collaborators in the debris of first hydrogen bomb explosion in 1952.

See also: Named after Albert Einstein, → einstein + → -ium.