Einsteinium

Chaitra 26/06/2026 19:58:09 Updated 26/06/2026 19:58:09

Property	Value
Atomic Number	99
Element	Einsteinium
Symbol	Es
Atomic Mass	[252] (most stable isotope)
Number of Neutrons	153 (Einsteinium-252)
Number of Protons	99
Number of Electrons	99
Period	7
Group	Actinide (no fixed group number)
Phase	Solid
Radioactive	Yes
Natural	No (synthetic element)
Metal	Yes
Nonmetal	No
Metalloid	No
Type	Actinide
Atomic Radius	~186 pm (estimated)
Electronegativity	1.30 (estimated)
First Ionization Energy	6.42 eV (estimated)
Density	~8.84 g/cm³ (estimated)
Melting Point	860 °C
Boiling Point	— (not well established)
Number of Isotopes	No stable isotopes (Es-252 most notable)
Discoverer	Albert Ghiorso and team
Year	1952
Specific Heat	— (not well established)
Number of Shells	7
Number of Valence Electrons	3