Einsteinium

 Royal Society of Chemistry: Einsteinium

Einsteinium was discovered in the debris of the first thermonuclear explosion which took place on a Pacific atoll, on 1 November 1952. Fall-out material, gathered from a neighbouring atoll, was sent to Berkeley, California, for analysis. There it was examined by Gregory Choppin, Stanley Thompson, Albert Ghiorso, and Bernard Harvey. Within a month they had discovered and identified 200 atoms of a new element, einsteinium, but it was not revealed until 1955.