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What is Einsteinium

Einsteinium (pronounced as ine-STINE-ee-em) is a radioactive metal, belonging to the family of transuranium elements, and denoted by the chemical symbol Es. It has 16 isotopes out of which einsteinium-252 is the most stable one with a half-life of 47.1 days [2, 3].

History of Einsteinium

Origin of its Name

The element is named after the renowned German physicist, Albert Einstein [1, 2].

Who Discovered Einsteinium

In 1952, a team of scientists led by American nuclear scientist Albert Ghiorso, discovered it [2].

When and Where was it Discovered

On 1st November 1952, a thermonuclear bomb explosion had been conducted on a small island near the Pacific Coast. After which, the residual radioactive material collected from the neighboring atoll was sent to Berkeley, California for examination. After a month of thorough analysis of the debris, done by Ghiorso and his teammates Stanley Thompson, Gregory Choppin, and Bernard Harvey, 200 atoms of einsteinium were discovered. Einsteinium-253 with a half-life of about 20 days was the isotope found from the debris that formed during the explosion when Uranium-238 underwent bombardment with neutrons and went through a chain of several decay reactions. However, nothing was officially revealed until 1955, due to security reasons [2, 4].


Classification and Position of Einsteinium on the Periodic Table [2]

Group Number Unknown
Group Name Actinides
Period 7
Block f

Properties of Einsteinium [1, 2, 3]

General Properties

Relative Atomic Mass 252

Physical Properties

Color/Appearance Unknown
Luster Unknown
Odor Unknown
Melting Point/Freezing Point (°C/°F ) 860/1580
Boiling Point (°C) Unknown
Density (g/cm3) Unknown
State of Matter at Room Temperature (solid/liquid/gas) Solid
Hardness (Mohs) Unknown
Electrical Conductivity (Sm-1) Unknown
Thermal (Heat) Conductivity (W m-1 K-1) Unknown

Chemical Properties

Flammability Unknown
Oxidation Number +3

Atomic Data of the Element [1, 2, 3]

Atomic Number 99
Valence Electrons 2
Quantum Numbers
– n 5
– ℓ 3
– m 0
– m s -1/2
Electron Configuration (Noble Gas Configuration) [Rn] 5f117s2
Atomic Structure
– Number of Electrons 99
– Number of Neutrons 153
– Number of Protons 99
Radius of Atom
– Atomic Radius (Å) 2.45
– Covalent Radius (Å) 1.65
Electronegativity Unknown
Ionization Energy


1st 2nd 3rd 4th 5th 6th 7th
619.44 1158

Einsteinium Bohr Model

What is Einsteinium Used for

Apart from basic scientific research, related to study of its properties, and production of other elements with a higher atomic number, Es has no commercial applications [2, 5].

Interesting Facts

  • The element was casually referred to as pandamonium by the team of discoverers before getting its official name, as the bomb testing experiment was code-named Project Panda [5].
  • The symbol of einsteinium was initially proposed as E, but IUPAC changed it to Es [5].
  • In 1955, the element was used to synthesize the first sample of the mendelevium [3].

Cost of Einsteinium

Since the element is synthetically produced in minute amounts, it cannot be found outside laboratory production.



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