Einsteinium Einsteinium is a synthetic element with the symbol Es and atomic number 99. Einsteinium is a member of the actinide series and it is the seventh transuranium element. It was named in honor of Albert Einstein. Einsteinium was discovered as a compo ...

(₉₉Es) is a

synthetic element A synthetic element is one of 24 known chemical elements that do not occur naturally on Earth: they have been created by human manipulation of fundamental particles in a nuclear reactor, a particle accelerator, or the explosion of an atomic bomb; ...

, and thus a

standard atomic weight The standard atomic weight of a chemical element (symbol ''A''r°(E) for element "E") is the weighted arithmetic mean of the relative isotopic masses of all isotopes of that element weighted by each isotope's abundance on Earth. For example, is ...

cannot be given. Like all synthetic elements, it has no

stable isotope The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundanc ...

s. The first

isotope Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numbers) ...

to be discovered (in nuclear

fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioac ...

from the

Ivy Mike Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion. Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in ...

H-bomb A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

) was ²⁵³Es in 1952. There are 18 known

radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

s from ²⁴⁰Es to ²⁵⁷Es, and 3

nuclear isomer A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy excited state, higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited ...

s (^250mEs, ^254mEs, and ^256mEs). The longest-lived isotope is ²⁵²Es with a

half-life Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...

of 471.7 days, or around 1.293 years.

List of isotopes

, - , rowspan=2, ²⁴⁰Es , rowspan=2 style="text-align:right" , 99 , rowspan=2 style="text-align:right" , 141 , rowspan=2, 240.06892(43)# , rowspan=2, 6(2) s , α , ²³⁶Bk , rowspan=2, , - , β⁺ (rare) , ²⁴⁰Cf , - , rowspan=2, ²⁴¹Es , rowspan=2 style="text-align:right" , 99 , rowspan=2 style="text-align:right" , 142 , rowspan=2, 241.06854(24)# , rowspan=2, 10(5) s
(+6−5) s, α , ²³⁷Bk , rowspan=2, (3/2−) , - , β⁺ (rare) , ²⁴¹Cf , - , rowspan=3, ²⁴²Es , rowspan=3 style="text-align:right" , 99 , rowspan=3 style="text-align:right" , 143 , rowspan=3, 242.06975(35)# , rowspan=3, 13.5(25) s , α (99.94%) , ²³⁸Bk , rowspan=3, , - , β⁺, SF (.6%) , (various) , - , β⁺ (rare) , ²⁴²Cf , - , rowspan=2, ²⁴³Es , rowspan=2 style="text-align:right" , 99 , rowspan=2 style="text-align:right" , 144 , rowspan=2, 243.06955(25)# , rowspan=2, 21(2) s , β⁺ (70%) , ²⁴³Cf , rowspan=2, 3/2−# , - , α (30%) , ²³⁹Bk , - , rowspan=3, ²⁴⁴Es , rowspan=3 style="text-align:right" , 99 , rowspan=3 style="text-align:right" , 145 , rowspan=3, 244.07088(20)# , rowspan=3, 37(4) s , β⁺ (94.69%) , ²⁴⁴Cf , rowspan=3, , - , α (5.3%) , ²⁴⁰Bk , - , β⁺, SF (.01%) , (various) , - , rowspan=2, ²⁴⁵Es , rowspan=2 style="text-align:right" , 99 , rowspan=2 style="text-align:right" , 146 , rowspan=2, 245.07132(22)# , rowspan=2, 1.1(1) min , β⁺ (60%) , ²⁴⁵Cf , rowspan=2, (3/2−) , - , α (40%) , ²⁴¹Bk , - , rowspan=3, ²⁴⁶Es , rowspan=3 style="text-align:right" , 99 , rowspan=3 style="text-align:right" , 147 , rowspan=3, 246.07290(24)# , rowspan=3, 7.7(5) min , β⁺ (90.1%) , ²⁴⁶Cf , rowspan=3, 4−# , - , α (9.9%) , ²⁴²Bk , - , β⁺, SF (.003%) , (various) , - , rowspan=3, ²⁴⁷Es , rowspan=3 style="text-align:right" , 99 , rowspan=3 style="text-align:right" , 148 , rowspan=3, 247.07366(3)# , rowspan=3, 4.55(26) min , β⁺ (93%) , ²⁴⁷Cf , rowspan=3, 7/2+# , - , α (7%) , ²⁴³Bk , - , SF (9×10⁻⁵%) , (various) , - , rowspan=3, ²⁴⁸Es , rowspan=3 style="text-align:right" , 99 , rowspan=3 style="text-align:right" , 149 , rowspan=3, 248.07547(6)# , rowspan=3, 27(5) min , β⁺ (99.75%) , ²⁴⁸Cf , rowspan=3, 2−#, 0+# , - , α (.25%) , ²⁴⁴Bk , - , β⁺, SF (3×10⁻⁵%) , (various) , - , rowspan=2, ²⁴⁹Es , rowspan=2 style="text-align:right" , 99 , rowspan=2 style="text-align:right" , 150 , rowspan=2, 249.07641(3)# , rowspan=2, 102.2(6) min , β⁺ (99.43%) , ²⁴⁹Cf , rowspan=2, 7/2+ , - , α (.57%) , ²⁴⁵Bk , - , rowspan=2, ²⁵⁰Es , rowspan=2 style="text-align:right" , 99 , rowspan=2 style="text-align:right" , 151 , rowspan=2, 250.07861(11)# , rowspan=2, 8.6(1) h , β⁺ (97%) , ²⁵⁰Cf , rowspan=2, (6+) , - , α (3%) , ²⁴⁶Bk , - , rowspan=2 style="text-indent:1em" , ^250mEs , rowspan=2 colspan="3" style="text-indent:2em" , 200(150)# keV , rowspan=2, 2.22(5) h , EC (99%) , ²⁵⁰Cf , rowspan=2, 1(−) , - , α (1%) , ²⁴⁶Bk , - , rowspan=2, ²⁵¹Es , rowspan=2 style="text-align:right" , 99 , rowspan=2 style="text-align:right" , 152 , rowspan=2, 251.079992(7) , rowspan=2, 33(1) h , EC (99.51%) , ²⁵¹Cf , rowspan=2, (3/2−) , - , α (.49%) , ²⁴⁷Bk , - , rowspan=3, ²⁵²Es , rowspan=3 style="text-align:right" , 99 , rowspan=3 style="text-align:right" , 153 , rowspan=3, 252.08298(5) , rowspan=3, 471.7(19) d , α (76%) , ²⁴⁸Bk , rowspan=3, (5−) , - , EC (24%) , ²⁵²Cf , - , β⁻ (.01%) , ²⁵²Fm , - , rowspan=2, ²⁵³EsMost common isotope , rowspan=2 style="text-align:right" , 99 , rowspan=2 style="text-align:right" , 154 , rowspan=2, 253.0848247(28) , rowspan=2, 20.47(3) d , α , ²⁴⁹Bk , rowspan=2, 7/2+ , - , SF (8.7×10⁻⁶%) , (various) , - , rowspan=4, ²⁵⁴Es , rowspan=4 style="text-align:right" , 99 , rowspan=4 style="text-align:right" , 155 , rowspan=4, 254.088022(5) , rowspan=4, 275.7(5) d , α , ²⁵⁰Bk , rowspan=4, (7+) , - , EC (10⁻⁴%) , ²⁵⁴Cf , - , SF (3×10⁻⁶%) , (various) , - , β⁻ (1.74×10⁻⁶%) , ²⁵⁴Fm , - , rowspan=5 style="text-indent:1em" , ^254mEs , rowspan=5 colspan="3" style="text-indent:2em" , 84.2(25) keV , rowspan=5, 39.3(2) h , β⁻ (98%) , ²⁵⁴Fm , rowspan=5, 2+ , - , IT (3%) , ²⁵⁴Es , - , α (.33%) , ²⁵⁰Bk , - , EC (.078%) , ²⁵⁴Cf , - , SF (.0045%) , (various) , - , rowspan=3, ²⁵⁵Es , rowspan=3 style="text-align:right" , 99 , rowspan=3 style="text-align:right" , 156 , rowspan=3, 255.090273(12) , rowspan=3, 39.8(12) d , β⁻ (92%) , ²⁵⁵Fm , rowspan=3, (7/2+) , - , α (8%) , ²⁵¹Bk , - , SF (.0041%) , (various) , - , ²⁵⁶Es , style="text-align:right" , 99 , style="text-align:right" , 157 , 256.09360(11)# , 25.4(24) min , β⁻ , ²⁵⁶Fm , (1+, 0−) , - , rowspan=2 style="text-indent:1em" , ^256mEs , rowspan=2 colspan="3" style="text-indent:2em" , 0(100)# keV , rowspan=2, 7.6 h , β⁻ (99.99%) , ²⁵⁶Fm , rowspan=2, (8+) , - , β⁻, SF (.002%) , (various) , - , rowspan=2, ²⁵⁷Es , rowspan=2 style="text-align:right" , 99 , rowspan=2 style="text-align:right" , 158 , rowspan=2, 257.09598(44)# , rowspan=2, 7.7(2) d , β⁻ , ²⁵⁷Fm , rowspan=2, 7/2+# , - , α , ²⁵³Bk

References

* Isotope masses from: ** * Isotopic compositions and standard atomic masses from: ** ** * Half-life, spin, and isomer data selected from the following sources. ** ** ** {{Navbox element isotopes Einsteinium