Einsteinium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements

99 californium ← einsteinium → fermium Ho ↑ Es ↓ (Uqe) Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	einsteinium, Es, 99
Chemical series	actinides
Group, Period, Block	n/a, 7, f
Appearance	unknown, probably silvery white or metallic gray
Atomic mass	(252) g/mol
Electron configuration	[Rn] 5f11 7s2
Electrons per shell	2, 8, 18, 32, 29, 8, 2
Physical properties
Phase	solid
Density (near r.t.)	8.84 g·cm−3
Melting point	1133  K (860 ° C, 1580 ° F)
Atomic properties
Electronegativity	1.3 (Pauling scale)
Ionization energies	1st: 619 kJ/mol
Miscellaneous
Magnetic ordering	no data
CAS registry number	7429-92-7
Selected isotopes
Main article: Isotopes of einsteinium iso NA half-life DM DE ( MeV) DP 252Es syn 471.7 d α 6.760 248Bk ε 1.260 252Cf β- 0.480 252Fm 253Es syn 20.47 d SF - - α 6.739 249Bk 254Es syn 275.7 d ε 0.654 254Cf β- 1.090 254Fm α 6.628 250Bk 255Es syn 39.8 d β- 0.288 255Fm α 6.436 251Bk SF - -
References

Einsteinium ( IPA: /ˌʌɪnˈstʌɪniəm/) is a synthetic element in the periodic table that has the symbol Es and atomic number 99. A metallic highly radioactive transuranic element (7th in the series) in the actinides, einsteinium is produced by bombarding plutonium with neutrons and was discovered in the debris of the first hydrogen bomb test. It was named after Albert Einstein and has no known uses. Tracer studies using the isotope ²⁵³Es show that einsteinium has chemical properties typical of a heavy trivalent, actinide element.

History

Einsteinium was first identified in December 1952 by Albert Ghiorso at the University of California, Berkeley and another team headed by G.R. Choppin at Los Alamos National Laboratory. Both were examining debris from the first hydrogen bomb test of November 1952 (see Operation Ivy). They discovered the isotope ²⁵³Es ( half-life 20.5 days) that was made by the nuclear fusion of 15 neutrons with ²³⁸U (which then went through seven beta decays). These findings were kept secret until 1955 due to Cold War tensions, however.

In 1961, enough einsteinium was synthesized to prepare a macroscopic amount of ²⁵³Es. This sample weighed about 0.01 mg and was measured using a special balance. The material produced was used to produce mendelevium. Further einsteinium has been produced at the Oak Ridge National Laboratory's High Flux Isotope Reactor in Tennessee by bombarding ²³⁹Pu with neutrons. Around 3 mg was created over a four year program of irradiation and then chemical separation from a starting 1 kg of plutonium isotope.

Isotopes

19 radioisotopes of einsteinium have been characterized, with the most stable being ²⁵²Es with a half-life of 471.7 days, ²⁵⁴Es with a half-life of 275.7 days, ²⁵⁵Es with a half-life of 39.8 days, and ²⁵³Es with a half-life of 20.47 days. All of the remaining radioactive isotopes have half-lifes that are less than 40 hours, and the majority of these have half lifes that are less than 30 minutes. This element also has 3 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

• EsBr₂ einsteinium(II) bromide

• 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