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 ↓ — 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	common: +3 +2, +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
Main isotopes 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 –

Einsteinium (/aɪnˈstaɪniəm/ eyen-STYE-nee-əm) is a metallic synthetic element. On the periodic table, it is represented by the symbol Es and atomic number 99. It is the seventh transuranic element, and an actinide. It was named in honor of Albert Einstein.

Its position on the periodic table indicates that its chemical and physical properties are similar to other metals. Though only small amounts have been made, it has been determined to be silver-colored. According to tracer studies conducted at Los Alamos National Laboratory using the isotope ²⁵³Es, this element has chemical properties typical of a heavy trivalent, actinide element.

Like all synthetic elements, isotopes of einsteinium are extremely radioactive and are considered highly toxic.

Production

Einsteinium does not occur naturally in any measurable quantities. The modern process of creating the element starts with the irradiation of plutonium-239 in a nuclear reactor for several years. The resulting plutonium-242 isotope (in the form of the compound plutonium(IV) oxide) is mixed with aluminium and formed into pellets. The pellets are then further irradiated for approximately one year in a nuclear reactor. Another four months of irradiation is required in a different reactor. The result is a mixture of californium and einsteinium, which can then be separated.

Uses

Aside from basic scientific research (such as being a step in the production of other elements), einsteinium has no known uses.

Isotopes

Nineteen radioisotopes of einsteinium have been characterized, with the most stable being ²⁵²Es with a half-life of 471.7 days. ²⁵⁴Es has a half-life of 275.7 days, ²⁵⁵Es 39.8 days and ²⁵³Es 20.47 days. All of the remaining radioactive isotopes have half-lives that are less than 40 hours, the majority of these having half-lives that are less than 30 minutes. This element also has three meta states, with the most stable being ^254mEs (t_½ = 39.3 hours). The isotopes of einsteinium range in atomic mass from 240.069 u (²⁴⁰Es) to 258.100 u (²⁵⁸Es).

Known compounds

File:Es triiodide transmitted light b.jpg

Einsteinium iodide EsI₃ in transmitted light

The following is a list of known compounds of einsteinium:

• EsBr₃ einsteinium(III) bromide
• EsCl₂ einsteinium(II) chloride
• EsCl₃ einsteinium(III) chloride
• EsF₃ einsteinium(III) fluoride
• EsI₂ einsteinium(II) iodide
• EsI₃ einsteinium(III) iodide
• Es₂O₃ einsteinium(III) oxide

History

Einsteinium was first identified in December 1952 by Albert Ghiorso and co-workers at the University of California at Berkeley. They were examining debris from the first hydrogen bomb test, which took place on November 1, 1952 (see the Ivy Mike H-bomb test). They discovered the isotope ²⁵³Es (half-life 20.5 days) that was made by the capture of 15 neutrons by uranium-238 nuclei – which then underwent seven successive beta decays).

$\mathrm {^{238}_{\ 92}U\ {\xrightarrow {+\ 15n}}\ _{\ 92}^{253}U\ {\xrightarrow {\beta ^{-}}}\ _{\ 93}^{253}Np\ {\xrightarrow {\beta ^{-}}}\ _{\ 94}^{253}Pu\ {\xrightarrow {\beta ^{-}}}\ _{\ 95}^{253}Am\ {\xrightarrow {\beta ^{-}}}\ _{\ 96}^{253}Cm\ {\xrightarrow {\beta ^{-}}}\ _{\ 97}^{253}Bk\ {\xrightarrow {\beta ^{-}}}\ _{\ 98}^{253}Cf\ {\xrightarrow {\beta ^{-}}}\ _{\ 99}^{253}Es}$

These findings were kept secret until 1955 due to Cold War tensions. Some ²³⁸U atoms, however, could capture another amount of neutrons (most likely, 16 or 17):

$\mathrm {^{238}_{\ 92}U\ {\xrightarrow[{-7\ \beta ^{-}}]{+\ 15,\ 16,\ 17\ (n,\gamma )}}\ _{\ \ \ \ \ \ \ \ \ \ \ 99}^{253,\ 254,\ 255}Es}$

Isotopes of einsteinium were produced shortly afterward at the University of California Radiation Laboratory in a nuclear reaction between nitrogen-14 and uranium-238 nuclei. and later by intense neutron irradiation of plutonium in the Materials Testing Reactor.

In 1961, enough einsteinium was synthesized to prepare a microscopic amount of ²⁵³Es. This sample weighed about 10 micrograms, and it was weighed using a special balance. The material produced was used to produce mendelevium, element 101, by further nuclear reactions. More microscopic amounts of einsteinium have been produced at the Oak Ridge National Laboratory's High Flux Isotope Reactor in Oak Ridge, Tennessee, by bombarding plutonium-239 with neutrons. About three milligrams were created during a four-year program of irradiation and then chemical separation from a starting sample of one kg of plutonium.

Literature

• Stwertka, Albert (1996). A Guide to the Elements. Oxford Oxfordshire: Oxford University Press. ISBN 0195080831.
• Richard G. Haire: Einsteinium, in: Lester R. Morss, Norman M. Edelstein, Jean Fuger (Hrsg.): The Chemistry of the Actinide and Transactinide Elements, Springer, Dordrecht 2006; ISBN 1-4020-3555-1, p. 1577–1620.

External links

• It's Elemental - The Element Einsteinium
• WebElements.com - Einsteinium
• Albert Ghiorso about the discovery