# Isotopes of einsteinium
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{{Short description|none}}
{{Infobox einsteinium isotopes}}
[Einsteinium](/source/Einsteinium) (99Es) is a [synthetic element](/source/synthetic_element), and thus a [standard atomic weight](/source/standard_atomic_weight) cannot be given. Like all synthetic elements, it has no [stable isotope](/source/stable_isotope)s. The first [isotope](/source/isotope) to be discovered (in [nuclear fallout](/source/nuclear_fallout) from the [Ivy Mike](/source/Ivy_Mike) [H-bomb](/source/thermonuclear_weapon) [test](/source/nuclear_testing)) was 253Es in 1952. There are 18 known [radioisotope](/source/radioisotope)s, from 240Es to 257Es, and 8 [nuclear isomer](/source/nuclear_isomer)s. The longest-lived isotope is 252Es with a [half-life](/source/half-life) of 471.7 days or 1.291 years; the second longest, 254Es with half-life of 275.7 days is more available.
== List of isotopes ==
{{Anchor|Einsteinium-239|Einsteinium-258}}
{{Isotopes table
|symbol=Es
|refs=NUBASE2020, AME2020 II, IsotopeFRIB, IsomerFRIB
|notes=m, unc(), mass#, exen#, spin(), spin#, SF, EC, IT, discoveryname
}}
|-id=Einsteinium-240
| rowspan=3|240Es
| rowspan=3 style="text-align:right" | 99
| rowspan=3 style="text-align:right" | 141
| rowspan=3|240.06895(39)#
| rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/240.pdf 2017]
| rowspan=3|{{val|6.0|(17)|u=s}}
| [α](/source/alpha_decay) (70%)
| 236Bk
| rowspan=3|4−#
|-
| [β+](/source/beta_decay) (30%)
| 240Cf
|-
| β+, [SF](/source/Spontaneous_fission) (0.16%)
| (various)
|-id=Einsteinium-241
| 241Es
| style="text-align:right" | 99
| style="text-align:right" | 142
| 241.06859(25)#
| style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/241.pdf 1996]
| {{val|4.3|2.4|1.2|u=s}}[{{cite journal |last1=Khuyagbaatar |first1=J. |last2=Albers |first2=H. M. |last3=Block |first3=M. |last4=Brand |first4=H. |last5=Cantemir |first5=R. A. |last6=Di Nitto |first6=A. |last7=Düllmann |first7=Ch. E. |last8=Götz |first8=M. |last9=Götz |first9=S. |last10=Heßberger |first10=F. P. |last11=Jäger |first11=E. |last12=Kindler |first12=B. |last13=Kratz |first13=J. V. |last14=Krier |first14=J. |last15=Kurz |first15=N. |last16=Lommel |first16=B. |last17=Lens |first17=L. |last18=Mistry |first18=A. |last19=Schausten |first19=B. |last20=Uusitalo |first20=J. |last21=Yakushev |first21=A. |title=Search for Electron-Capture Delayed Fission in the New Isotope 244Md |journal=Physical Review Letters |date=1 October 2020 |volume=125 |issue=14 |article-number=142504 |doi=10.1103/PhysRevLett.125.142504 |pmid=33064498 |bibcode=2020PhRvL.125n2504K |s2cid=223546973 |url=http://urn.fi/URN:NBN:fi:jyu-202010066084 }}]
| α
| 237Bk
| 3/2−#
|-id=Einsteinium-242
| rowspan=3|242Es[{{cite journal | last1=Khuyagbaatar | first1=J. | last2=Cantemir | first2=R. A. | last3=Düllmann | first3=Ch. E. | last4=Jäger | first4=E. | last5=Kindler | first5=B. | last6=Krier | first6=J. | last7=Kurz | first7=N. | last8=Lommel | first8=B. | last9=Schausten | first9=B. | last10=Yakushev | first10=A. | title=Decay properties of the neutron-deficient isotope Es 242 | journal=Physical Review C | volume=109 | issue=3 | date=2024-03-18 | article-number=034311 | issn=2469-9985 | doi=10.1103/PhysRevC.109.034311| arxiv=2408.01714 }}]
| rowspan=3 style="text-align:right" | 99
| rowspan=3 style="text-align:right" | 143
| rowspan=3|242.06957(28)#
| rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/242.pdf 1994]
| rowspan=3|{{val|16.9|(8)|u=s}}
| β+
| 242Cf
| rowspan=3|2+#
|-
| α (41%)
| 238Bk
|-
| β+, SF (1.5%)
| (various)
|-id=Einsteinium-243
| rowspan=2|243Es
| rowspan=2 style="text-align:right" | 99
| rowspan=2 style="text-align:right" | 144
| rowspan=2|243.06951(22)#
| rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/243.pdf 1973]
| rowspan=2|{{val|22.1|(14)|u=s}}
| α (61%)
| 239Bk
| rowspan=2|(7/2+)
|-
| β+? (39%)
| 243Cf
|-id=Einsteinium-243m
| rowspan=3 style="text-indent:1em" | 243mEs[Order of ground state and isomer is uncertain.]
| rowspan=3 colspan=3 style="text-indent:2em" | 50(50)# keV
| rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/99/243Es-1.pdf 2025]
| rowspan=3|>50# μs
| [IT](/source/Isomeric_transition)?
| 243Es
| rowspan=3|3/2−#
|-
| α?
| 239Bk
|-
| β+?
| 243Cf
|-id=Einsteinium-244
| rowspan=3|244Es
| rowspan=3 style="text-align:right" | 99
| rowspan=3 style="text-align:right" | 145
| rowspan=3|244.07088(20)#
| rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/244.pdf 1973]
| rowspan=3|{{val|37|(4)|u=s}}
| β+ (95%)
| 244Cf
| rowspan=3|6+#
|-
| α (5%)
| 240Bk
|-
| β+, SF (0.011%)
| (various)
|-id=Einsteinium-245
| rowspan=2|245Es
| rowspan=2 style="text-align:right" | 99
| rowspan=2 style="text-align:right" | 146
| rowspan=2|245.07119(18)#
| rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/245.pdf 1967]
| rowspan=2|{{val|1.11|(6)|u=min}}
| β+ (51%)
| 245Cf
| rowspan=2|(3/2−)
|-
| α (49%)
| 241Bk
|-id=Einsteinium-245m
| rowspan=3 style="text-indent:1em" | 245mEs[Half-life not measured, not included in discovery database]
| rowspan=3|>50# μs
| [IT](/source/Isomeric_transition)?
| 245Es
| rowspan=3|7/2+#
|-
| α?
| 241Bk
|-
| β+?
| 245Cf
|-id=Einsteinium-246
| rowspan=3|246Es
| rowspan=3 style="text-align:right" | 99
| rowspan=3 style="text-align:right" | 147
| rowspan=3|246.07281(10)
| rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/246.pdf 1954]
| rowspan=3|{{val|7.5|(5)|u=min}}
| β+ (90.1%)
| 246Cf
| rowspan=3|4−#
|-
| α (9.9%)
| 242Bk
|-
| β+, SF (0.003%)
| (various)
|-id=Einsteinium-247
| rowspan=2|247Es
| rowspan=2 style="text-align:right" | 99
| rowspan=2 style="text-align:right" | 148
| rowspan=2|247.073622(21)
| rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/247.pdf 1967]
| rowspan=2|{{val|4.55|(26)|u=min}}
| β+ (93%)
| 247Cf
| rowspan=2|(7/2+)
|-
| α (7%)
| 243Bk
|-id=Einsteinium-247m
| rowspan=3 style="text-indent:1em" | 247mEs[Most common isotope]
| rowspan=2 style="text-align:right" | 99
| rowspan=2 style="text-align:right" | 154
| rowspan=2|253.0848212(13)
| rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/253.pdf 1954]
| rowspan=2|{{val|20.47|(3)|u=d}}
| α
| 249Bk
| rowspan=2|7/2+
|-
| SF (8.7×10−6%)
| (various)
|-id=Einsteinium-253m
| style="text-indent:1em" | 253mEs
| colspan=3 style="text-indent:2em" | 106(4) keV
| style="text-align:center" | (1993)[Theoretically capable of electron capture to 254Cf]
| 250Bk
| rowspan=3|7+
|-
| β− (1.74×10−4%)
| 254Fm
|-
| SF (<3×10−6%)
| (various)
|-id=Einsteinium-254m
| rowspan=5 style="text-indent:1em" | 254mEs
| rowspan=5 colspan="3" style="text-indent:2em" | 80.4(11) keV
| rowspan=5 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/99/254Es-1.pdf 1956]
| rowspan=5|{{val|39.3|(2)|u=h}}
| β− (98%)
| 254Fm
| rowspan=5|2+
|-
| IT (<3%)
| 254Es
|-
| α (0.32%)
| 250Bk
|-
| EC (0.076%)
| 254Cf
|-
| SF (<0.045%)
| (various)
|-id=Einsteinium-255
| rowspan=3|255Es
| rowspan=3 style="text-align:right" | 99
| rowspan=3 style="text-align:right" | 156
| rowspan=3|255.090274(12)
| rowspan=3 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/255.pdf 1954]
| rowspan=3|{{val|39.8|(12)|u=d}}
| β− (92.0%)
| 255Fm
| rowspan=3|(7/2+)
|-
| α (8.0%)
| 251Bk
|-
| SF (0.0041%)
| (various)
|-id=Einsteinium-256
| rowspan=2|256Es
| rowspan=2 style="text-align:right" | 99
| rowspan=2 style="text-align:right" | 157
| rowspan=2| 256.09360(11)#
| rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/99/256.pdf 1981]
| rowspan=2|{{val|7.6|u=h}}
| β−
| 256Fm
| rowspan=2|7+#
|-
| β−, SF (0.002%)
| (various)
|-id=Einsteinium-256m
| style="text-indent:1em" |256mEs