Einsteinium (99)

Einsteinium is radioactive rare earth metal named after Albert Einstein. It is of no commercial importance and only a few of its compounds are known.

Name: Einsteinium Symbol: Es Atomic number: 99 Atomic weight: [ 252 ] Standard state: solid at 298 K CAS Registry ID: 7429-92-7

Group name: Actinoid Period in periodic table: 7 (actinoid) Block in periodic table: f-block Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic

Historical information

Einsteinium was discovered by Workers at Argonne, Los Alamos, USA, and the University of California at Berkeley at 1952 in USA. Origin of name: named after "Albert Einstein".

Einsteinium was identified by Ghiorso and others (Berkeley, California, USA) in 1952 in radioactive debris from the first large thermonuclear bomb explosion, which took place in the Pacific in November 1952. In 1961, a sufficient amount of einsteinium was produced to permit separation of a macroscopic amount of ²⁵³Es.

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 procedure of separating einsteinium-253 from other actinides and products of their decay. Other isotopes are synthesized in various laboratories, but at much smaller amounts, by bombarding heavy actinide elements with light ions. Owing to the small amounts of produced einsteinium and the short half-life of its most easily produced isotope, there are currently almost no practical applications for it outside of basic scientific research. In particular, einsteinium was used to synthesize, for the first time, 17 atoms of the new element mendelevium in 1955.

In their discovery of the elements 99 and 100, the American teams had competed with a group at the Nobel Institute for Physics, Stockholm, Sweden. In late 1953 – early 1954, the Swedish group succeeded in the synthesis of light isotopes of element 100, in particular ²⁵⁰Fm, by bombarding uranium with oxygen nuclei. These results were also published in 1954. Nevertheless, the priority of the Berkeley team was generally recognized, as its publications preceded the Swedish article, and they were based on the previously undisclosed results of the 1952 thermonuclear explosion; thus the Berkeley team was given the privilege to name the new elements. As the effort which had led to the design of Ivy Mike was codenamed Project PANDA, element 99 had been jokingly nicknamed "Pandamonium" but the official names suggested by the Berkeley group derived from two prominent and recently deceased scientists, Albert Einstein (died 18 April 1955) and Enrico Fermi (died 28 November 1954):

"We suggest for the name for the element with the atomic number 99, einsteinium (symbol E) after Albert Einstein and for the name for the element with atomic number 100, fermium (symbol Fm), after Enrico Fermi."

The discovery of these new elements was announced by Albert Ghiorso at the first Geneva Atomic Conference held on 8–20 August 1955. The symbol for einsteinium was first given as "E" and later changed to "Es" by IUPAC (International Union of Pure and Applied Chemistry)

Physical properties

• Melting point: 1133 [or 860 °C (1580 °F)] K
• Boiling point: no data K
• Density of solid: 13500 kg m^-3

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 conversion to berkelium and then californium 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, and not in bulk. Einsteinium is the element with the highest atomic number which has been observed in macroscopic quantities in its pure form, and this was the common short-lived isotope einsteinium-253

Orbital properties

• Ground state electron configuration:  [Rn].5f¹¹.7s²
• Shell structure:  2.8.18.32.29.8.2
• Term symbol:   ⁵I_15/2
• Pauling electronegativity: 1.3 (Pauling units)
•  First ionization energy: 619 kJ mol^-1
• Second ionization energy: no data kJ mol^-1