Einsteinium

Einsteinium, ₉₉Es

Einsteinium
Pronunciation	/aɪnˈstaɪniəm/ ​(eyen-STY-nee-əm)
Appearance	silvery; glows blue in the dark
Mass number	[252]
Einsteinium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson Ho ↑ Es ↓ (Upt) californium ← einsteinium → fermium
Atomic number (Z)	99
Group	f-block groups (no number)
Period	period 7
Block	f-block
Electron configuration	[Rn] 5f11 7s2
Electrons per shell	2, 8, 18, 32, 29, 8, 2
Physical properties
Phase at STP	solid
Melting point	1133 K ​(860 °C, ​1580 °F)
Boiling point	1269 K ​(996 °C, ​1825 °F) (estimated)
Density (near r.t.)	8.84 g/cm3
Atomic properties
Oxidation states	+2, +3, +4
Electronegativity	Pauling scale: 1.3
Ionization energies	1st: 619 kJ/mol
Spectral lines of einsteinium
Other properties
Natural occurrence	synthetic
Crystal structure	​face-centered cubic (fcc)
Magnetic ordering	paramagnetic
CAS Number	7429-92-7
History
Naming	after Albert Einstein
Discovery	Lawrence Berkeley National Laboratory (1952)
Isotopes of einsteinium v e
Main isotopes[1] Decay abun­dance half-life (t1/2) mode pro­duct 252Es synth 471.7 d α 248Bk ε 252Cf β− 252Fm 253Es synth 20.47 d SF – α 249Bk 254Es synth 275.7 d ε 254Cf β− 254Fm α 250Bk 255Es synth 39.8 d β− 255Fm α 251Bk SF –
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Einsteinium is a synthetic chemical element; it has symbol Es and atomic number 99. It is a member of the actinide series and it is the seventh transuranium element. It was named in honor of Albert Einstein.

Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952. Its most common isotope, einsteinium-253 (half-life 20.47 days), is produced artificially from decay of californium-253 in a few dedicated high-power nuclear reactors with a total yield on the order of one milligram per year. The reactor synthesis is followed by a complex process of separating einsteinium-253 from other actinides and products of their decay. Other isotopes are synthesized in various laboratories, but in much smaller amounts, by bombarding heavy actinide elements with light ions. Due to the small amounts of produced einsteinium and the short half-life of its most common isotope, there are no practical applications for it except basic scientific research. In particular, einsteinium was used to synthesize, for the first time, 17 atoms of the new element mendelevium in 1955.

Einsteinium is a soft, silvery, paramagnetic metal. Its chemistry is typical of the late actinides, with a preponderance of the +3 oxidation state; the +2 oxidation state is also accessible, especially in solids. The high radioactivity of einsteinium-253 produces a visible glow and rapidly damages its crystalline metal lattice, with released heat of about 1000 watts per gram. Difficulty in studying its properties is due to einsteinium-253's decay to berkelium-249 and then californium-249 at a rate of about 3% per day. The isotope of einsteinium with the longest half-life, einsteinium-252 (half-life 471.7 days) would be more suitable for investigation of physical properties, but it has proven far more difficult to produce and is available only in minute quantities, not in bulk.^[2] Einsteinium is the element with the highest atomic number which has been observed in macroscopic quantities in its pure form as einsteinium-253.^[3]

Like all synthetic transuranium elements, isotopes of einsteinium are very radioactive and are considered highly dangerous to health on ingestion.^[4]