Einsteinium (Es)

Einsteinium is a chemical element with an atomic number of 99 in the periodic table of elements. It’s a synthetically produced substance that has not been found in Earth’s crust. Being a member of the actinide elements family of the periodic table, this transuranium element has three valence electrons and emits extremely high radiation. 

Fact Box

Chemical and Physical Properties of Einsteinium

The symbol in the periodic table of elements: Es

Atomic number: 99

Atomic weight (mass): 254 g.mol-1

Group number: 20 (Actinides)

Period: 7

Color: Silver-colored (based upon an assumption)

Physical state: Solid at 20°C

Half-life: From 2 seconds (257Es) up to 471 days (252Es)

Electronegativity according to Pauling: N/A

Density: Unknown phase at room temperature

Melting point: 860°C, 1580°F, 1133 K

Boiling point: N/A

Van der Waals radius: N/A

Ionic radius: N/A

Isotopes: 18

Most characteristic isotope: 252Es 

Electronic shell: [Rn] 5f117s2 

The energy of the first ionization: N/A

The energy of the second ionization: N/A

Discovery date: In 1952 by Albert Ghiorso, Gregory Choppin, Stanley Thompson, and Bernard Harvey

Einsteinium is the seventh transuranic element classified as a member of the actinide series.  With the periodic table symbol Es, atomic number 99, atomic mass of 254 g.mol-1, atomic radius 186 pm, and electron configuration [Rn] 5f117s2, this synthetic radioactive and paramagnetic metal reaches its melting point at 860°C (1580°F, 1133 K).

This actinide element of the periodic table shares many chemical properties with the other elements of the group, especially with the actinide fermium and the lanthanide holmium. It readily reacts with oxygen, steam, and acids, but is unreactive with alkalis, and has a preponderance of both the +3 and +2 oxidation states.           

How Was Einsteinium Discovered?

After the first thermonuclear explosion was conducted by the United States on 1 November 1952 at the Bikini Atoll lagoon, the Marshall Islands in the Pacific Ocean, the debris produced by the detonation of the first hydrogen bomb. This hydrogen bomb test after World War II proved to be a rich source of new chemical elements. 

Namely, the team of scientists working at the University of California, Berkeley, led by the American chemist Albert Ghiorso, and another team led by G. R. Choppin at Argonne, Los Alamos, conducted scientific research in order to isolate all elements that have occurred in the debris. By employing several techniques, both teams of scientists succeeded in discovering more than 200 atoms of einsteinium-253 isotope after a month-long research and examination of the debris sample. It was produced by the nuclear fusion of 15 neutrons with 238 U that have undergone seven beta decays. The half-life of the discovered einsteinium isotope was 20.5 days. 

Since the controlled explosion of the first hydrogen bomb was a part of an experiment, the findings of these researches, along with the discovery of the new chemical element, were kept secret for more than three years. 

In 1961, the teams of scientists managed to produce a few micrograms of einsteinium-253, i.e. just enough so that it can be visible to the naked eye. This radioactive substance was used in the production of the chemical element mendelevium. In addition, the scientists at the Oak Ridge National Laboratory continued the production of this radioactive metal by employing the processes of irradiation and chemical separation from a starting quantity of 1 kg plutonium isotope. 

How Did Einsteinium Get Its Name?

This chemical element was named after the most ingenious mind in the field of physics, Albert Einstein. The legendary scientist was honored upon the suggestion of the discoverer of einsteinium, Albert Ghiorso, and his colleagues, for Einstein’s great achievements in the quantum theory realm. Most importantly, Einstein postulated the conversion of mass to energy in the world’s most destructive weapons. 

Where Can You Find Einsteinium?

Since einsteinium is a highly radioactive man-made chemical element, it can be obtained in milligram quantities by neutron bombardment of plutonium in a nuclear reactor. The process of einsteinium production begins with irradiation of plutonium-239 in a nuclear reactor for several years, which results in plutonium-242 isotope (in the form of the plutonium(IV) oxide compound). 

After this, the produced isotopes are combined with aluminum and formed into pellets that are further exposed to the irradiation process in a nuclear reactor. This stage lasts for about a year. In the final stage of production, the material is exposed to radiation for another four months in a different nuclear reactor. From the resulting mixture of californium and einsteinium, both of these elements can be isolated in their elemental form. 

Einsteinium in Everyday Life

Einsteinium is used as a component for the production of some of the heavier chemical elements, such as mendelevium. Namely, this chemical element is produced by bombarding einsteinium-253 targets with alpha particles in cyclotrons or linear accelerators. 

There are no other known applications of this radioactive man-made element since only a few milligrams of einsteinium are produced each year. It took nine whole years for the scientists to succeed in producing a visible quantity of this transuranium element. 

How Dangerous Is Einsteinium?

By being highly radioactive, einsteinium is classified as a highly dangerous substance. Its radioactivity imposes a severe health hazard.

Environmental Effects of Einsteinium

Despite being a synthetically produced element, einsteinium can still be found in the environment as debris from nuclear explosions or at nuclear test sites. However, due to the fact that it doesn’t occur naturally in Earth’s crust, this radioactive chemical cannot be considered an environmental hazard. 

Isotopes of Einsteinium

Being a highly radioactive chemical element, einsteinium has no stable isotopes. Among the eighteen known radioisotopes, einsteinium-252 is the longest-lived isotope with a half-life ranging from 471.7 days to 1.293 years. This einsteinium isotope decays into berkelium-248 through alpha decay, or into californium-252 via electron capture.


[n 1]

Z N Isotopic mass (Da)

[n 2][n 3]

Half-life Decay


[n 4]



Spin and


[n 5][n 6]

Excitation energy[n 6]
240Es 99 141 240.06892(43)# 6(2) s[1] α 236Bk
β+ (rare) 240Cf
241Es 99 142 241.06854(24)# 10(5) s

[8(+6−5) s]

α 237Bk (3/2−)
β+ (rare) 241Cf
242Es 99 143 242.06975(35)# 13.5(25) s α (99.94%) 238Bk
β+, SF (.6%) (various)
β+ (rare) 242Cf
243Es 99 144 243.06955(25)# 21(2) s β+ (70%) 243Cf 3/2−#
α (30%) 239Bk
244Es 99 145 244.07088(20)# 37(4) s β+ (94.69%) 244Cf
α (5.3%) 240Bk
β+, SF (.01%) (various)
245Es 99 146 245.07132(22)# 1.1(1) min β+ (60%) 245Cf (3/2−)
α (40%) 241Bk
246Es 99 147 246.07290(24)# 7.7(5) min β+ (90.1%) 246Cf 4−#
α (9.9%) 242Bk
β+, SF (.003%) (various)
247Es 99 148 247.07366(3)# 4.55(26) min β+ (93%) 247Cf 7/2+#
α (7%) 243Bk
SF (9×10−5%) (various)
248Es 99 149 248.07547(6)# 27(5) min β+ (99.75%) 248Cf 2−#, 0+#
α (.25%) 244Bk
β+, SF (3×10−5%) (various)
249Es 99 150 249.07641(3)# 102.2(6) min β+ (99.43%) 249Cf 7/2+
α (.57%) 245Bk
250Es 99 151 250.07861(11)# 8.6(1) h β+ (97%) 250Cf (6+)
α (3%) 246Bk
251Es 99 152 251.079992(7) 33(1) h EC (99.51%) 251Cf (3/2−)
α (.49%) 247Bk
252Es 99 153 252.08298(5) 471.7(19) d α (76%) 248Bk (5−)
EC (24%) 252Cf
β (.01%) 252Fm
253Es[n 7] 99 154 253.0848247(28) 20.47(3) d α 249Bk 7/2+
SF (8.7×10−6%) (various)
254Es 99 155 254.088022(5) 275.7(5) d α 250Bk (7+)
EC (10−4%) 254Cf
SF (3×10−6%) (various)
β (1.74×10−6%) 254Fm
255Es 99 156 255.090273(12) 39.8(12) d β (92%) 255Fm (7/2+)
α (8%) 251Bk
SF (.0041%) (various)
256Es 99 157 256.09360(11)# 25.4(24) min β 256Fm (1+, 0−)
257Es 99 158 257.09598(44)# 7.7(2) d β 257Fm 7/2+#
α 253Bk

Source: Wikipedia

List of Einsteinium Compounds

Einsteinium typically forms oxides, halides, as well as organo-einsteinium compounds. The list of the most common einsteinium compounds incorporates:

  • 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]

5 Interesting Facts and Explanations

  1. The 100th element of the periodic table, fermium, was also discovered in the debris after the detonation of the first hydrogen bomb. 
  2. A hydrogen bomb is a weapon that derives enormous energy from the nuclear fusion of hydrogen isotopes.
  3. Quantum theory is a theory of matter and energy that explains the way atoms interact on both atomic and subatomic levels. This theory serves as the basis of all quantum physics including quantum chemistry, quantum field theory, quantum technology, and quantum information science.
  4. Albert Einstein is indirectly responsible for the creation of the atomic bomb due to his scientific input.
  5. The first nuclear explosion that was conducted by the United States was five hundred times stronger than the destructive power of the nuclear bomb that destroyed the southern Japanese town of Nagasaki, on August 9, 1945.