Einsteinium - Es General Information Discovery Einsteinium was discovered by G.R. Choppin, S.G. Thompson, A Ghiorso and B.G. Harvey in 1952, in the debris of the thermonuclear explosion in the Pacific at Eniwetok. This involved the examination of tons of radioactive coral from the blast area. Appearance Einsteinium is a radioactive, silvery metal. Source Einsteinium can be obtained in milligram quantities from the neutron bombardment of plutonium. Uses Einsteinium has no uses outside research. Biological Role Einsteinium has no known biological role. It is toxic due to its radioactivity. General Information Einsteinium is attacked by oxygen, steam and acids but not by alkalis.

	Physical Information
	Atomic Number		99
	Relative Atomic Mass (12C=12.000)		254 (radioactive)
	Melting Point/K		not available
	Boiling Point/K		not available
	Density/kg m-3		not available
	Ground State Electron Configuration		[Rn]5f117s2
	Electron Affinity(M-M-)/kJ mol-1		-50

	Key Isotopes
	nuclide	253Es	254Es
	atomic mass		254.09
	natural abundance	0%	0%
	half-life	20.7 days	201 days

Other Information
Enthalpy of Fusion/kJ mol-1		n/a
Enthalpy of Vaporisation/kJ mol-1		n/a
Oxidation States
main	Es+3
others	Es+2

	Ionisation Energies/kJ mol-1
	M - M+	619
	M+ - M2+
	M2+ - M3+
	M3+ - M4+
	M4+ - M5+
	M5+ - M6+
	M6+ - M7+
	M7+ - M8+
	M8+ - M9+
	M9+ - M10+