View source for Isotopes of beryllium

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{{more citations needed|date=May 2018}}
{{Infobox beryllium isotopes}}
<!-- 
Note: Please change it so that it says that beryllium-8 decays into 2x helium-4, not 1x, since helium-4 is an alpha particle, and another helium-4 is left. Remove this note when this has been done. The *product"is helium-4, so it is correct. This is not the reaction formula (which should balance) -->

[[Beryllium]] (<sub>4</sub>Be) has 11 known [[Isotope|isotopes]] and 3 known [[nuclear isomer|isomers]], but only one of these isotopes ({{SimpleNuclide|Beryllium|9}}) is stable and a [[primordial nuclide]].  As such, beryllium is considered a [[monoisotopic element]]. It is also a [[mononuclidic element]], because its other isotopes have such short half-lives that none are primordial and their abundance is very low ([[standard atomic weight]] is {{val|9.0121831|(5)}}). Beryllium is unique as being the only monoisotopic element with both an even number of [[proton]]s and an odd number of [[neutron]]s. There are 25 other monoisotopic elements but all have odd atomic numbers, and even numbers of neutrons.

Of the 10 [[radionuclide|radioisotopes]] of beryllium, the most stable are {{SimpleNuclide|Beryllium|10}} with a half-life of {{val|1.387|(12)}} million years{{refn|group=nb|name=tropical|Note that NUBASE2020 uses the <em>tropical</em> year to convert between years and other units of time, not the [[Gregorian year]]. The relationship between years and other time units in NUBASE2020 is as follows: {{nowrap|1=1 y = 365.2422 d = 31 556 926 s}} }} and {{SimpleNuclide|Beryllium|7}} with a half-life of {{val|53.22|(6)|u=days}}.  All other radioisotopes have half-lives under {{val|15|u=seconds}}, most under {{val|30|u=milliseconds}}. The least stable isotope is {{SimpleNuclide|Beryllium|16}}, with a half-life of {{val|650|(130)|u=yoctoseconds}}.

The 1:1 [[neutron–proton ratio]] seen in stable isotopes of many light elements (up to [[oxygen]], and in elements with even atomic number up to [[calcium]]) is prevented in beryllium by the extreme instability of {{SimpleNuclide|link=yes|Beryllium|8}} toward [[alpha decay]], which is favored due to the extremely tight binding of [[helium#Related stability of the helium-4 nucleus and electron shell|{{SimpleNuclide|Helium|4}}]] nuclei. The half-life for the decay of {{SimpleNuclide|Beryllium|8}} is only {{val|81.9|(3.7)|u=attoseconds}}.

Beryllium is prevented from having a stable isotope with 4 protons and 6 neutrons by the very lopsided neutron–proton ratio for such a light element. Nevertheless, this isotope, [[beryllium-10|{{SimpleNuclide|Beryllium|10}}]], has a half-life of {{val|1.387|(12)}} million years,{{refn|group=nb|name=tropical}} which indicates unusual stability for a light isotope with such a large neutron/proton imbalance. Other possible beryllium isotopes have even more severe mismatches in neutron and proton number, and thus are even less stable.

Most {{SimpleNuclide|Beryllium|9}} in the universe is thought to be formed by cosmic ray nucleosynthesis from [[cosmic ray spallation]] in the period between the [[Big Bang]] and the formation of the Solar System. The isotopes {{SimpleNuclide|Beryllium|7}}, with a half-life of {{val|53.22|(6)|u=d}}, and {{SimpleNuclide|Beryllium|10}} are both [[cosmogenic nuclide]]s because they are made on a recent timescale in the Solar System by spallation,<ref name="7Be-Mishra">{{Cite journal|last2=Marhas|first2=Kuljeet Kaur|last1=Mishra|first1=Ritesh Kumar|date=2019-03-25|title=Meteoritic evidence of a late superflare as source of 7 Be in the early Solar System|journal=Nature Astronomy|volume=3|issue=6|language=en|pages=498–505|doi=10.1038/s41550-019-0716-0|bibcode=2019NatAs...3..498M|s2cid=126552874|issn=2397-3366}}</ref> like [[carbon-14|{{SimpleNuclide|Carbon|14}}]].

== List of isotopes ==
{{Isotopes table
|symbol=Be
|refs=NUBASE2020, AME2020 II
|notes=m, resonance, unc(), mass#, spin(), daughter-st, EC, IT, n, p
}}
<!-- |-id=Beryllium-5
| {{SimpleNuclide|Beryllium|5}}<ref group="n" name="unconfirmed">This isotope has not yet been observed; given data is inferred or estimated from periodic trends.</ref>
|4
|1
| {{val|5.03987|(215)}}#
|
| [[proton emission|p]] ?<ref group="n" name="decay mode 1">Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide.</ref>
| {{SimpleNuclide|Lithium|4}} ?
| (1/2+)#
| -->
|-id=Beryllium-6
| {{SimpleNuclide|Beryllium|6}}<ref group="n">Intermediate in the [[proton–proton chain]]</ref>
|4
|2
| {{val|6.019726|(6)}}
| {{val|5.0|(3)|u=zs}}<br/>[{{val|91.6|(5.6)|u=keV}}]
| [[proton emission|2p]]
| '''{{SimpleNuclide|Helium|4}}'''
| 0+
|
|-
| {{SimpleNuclide|Beryllium|7}}<ref group="n">Produced in [[Big Bang nucleosynthesis]], but not primordial, as it all quickly decayed to '''<sup>7</sup>Li'''</ref>
|4
|3
| {{val|7.01692871|(8)}}
| {{val|53.22|(6)|u=d}}
| [[Electron capture|ε]]
| '''{{SimpleNuclide|Lithium|7}}'''
| 3/2−
| Trace<ref group="n" name="t">[[cosmogenic]] nuclide</ref>
|-
| [[Beryllium-8|{{SimpleNuclide|Beryllium|8}}]]<ref group="n">Intermediate product of [[triple alpha process]] in [[stellar nucleosynthesis]] as part of the path producing '''[[carbon-12|<sup>12</sup>C]]'''</ref>
|4
|4
| {{val|8.00530510|(4)}}
| {{val|81.9|(3.7)|u=as}}<br/>[{{val|5.58|(25)|u=eV}}]
| α<ref group="n">Also often considered [[spontaneous fission]], as {{SimpleNuclide|Beryllium|8}} splits into two equal {{SimpleNuclide|Helium|4}} nuclei</ref>
| '''{{SimpleNuclide|Helium|4}}'''
| 0+
|
|-id=Beryllium-8m
| style="text-indent:1em" | {{SimpleNuclide|Beryllium|8|m}}
| colspan="3" style="text-indent:2em" | {{val|16626|(3)|u=keV}}
| 
| α
| '''{{SimpleNuclide|Helium|4}}'''
| 2+
|
|-id=Beryllium-9
| {{SimpleNuclide|Beryllium|9}}
|4
|5
| {{val|9.01218306|(8)}}
| colspan=3 align=center|'''Stable'''
| 3/2−
| 1
|-id=Beryllium-9m
| style="text-indent:1em" | {{SimpleNuclide|Beryllium|9|m}}
| colspan="3" style="text-indent:2em" | {{val|14390.3|(1.7)|u=keV}}
| {{val|1.25|(10)|u=as}}<br/>[{{val|367|(30)|u=eV}}]
| 
| 
| 3/2−
|
|-
| [[Beryllium-10|{{SimpleNuclide|Beryllium|10}}]]
|4
|6
| {{val|10.01353469|(9)}}
| {{val|1.387|(12)|e=6|u=y}}{{refn|group=nb|name=tropical}}
| [[Beta decay|β<sup>−</sup>]]
| '''{{SimpleNuclide|Boron|10}}'''
| 0+
| Trace<ref group="n" name="t" />
|-id=Beryllium-11
| rowspan=3|{{SimpleNuclide|Beryllium|11}}<ref group="n">Has 1 [[halo nucleus|halo]] neutron</ref>
| rowspan=3|4
| rowspan=3|7
| rowspan=3|{{val|11.02166108|(26)}}
| rowspan=3|{{val|13.76|(7)|u=s}}
| β<sup>−</sup> ({{val|96.7|(1)|u=%}})
| '''{{SimpleNuclide|Boron|11}}'''
| rowspan=3|1/2+
| rowspan=3|
|-
| [[Alpha decay|β<sup>−</sup>α]] ({{val|3.3|(1)|u=%}})
| '''{{SimpleNuclide|Lithium|7}}'''
|-
| β<sup>−</sup>p ({{val|0.0013|(3)|u=%}})
| {{SimpleNuclide|Beryllium|10}}
|-id=Beryllium-11m
| style="text-indent:1em" | {{SimpleNuclide|Beryllium|11|m}}
| colspan="3" style="text-indent:2em" | {{val|21158|(20)|u=keV}}
| {{val|0.93|(13)|u=zs}}<br/>[{{val|500|(75)|u=keV}}]
| [[Nuclear isomer#Decay processes|IT]] ?<ref group="n" name="decay mode 1">Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide.</ref>
| {{SimpleNuclide|Beryllium|11}} ?
| 3/2−
|
|-id=Beryllium-12
| rowspan=2|{{SimpleNuclide|Beryllium|12}}
| rowspan=2|4
| rowspan=2|8
| rowspan=2|{{val|12.0269221|(20)}}
| rowspan=2|{{val|21.46|(5)|u=ms}}
| β<sup>−</sup> ({{val|99.50|(3)|u=%}})
| {{SimpleNuclide|Boron|12}}
| rowspan=2|0+
| rowspan=2|
|-
| β<sup>−</sup>n ({{val|0.50|(3)|u=%}})
| '''{{SimpleNuclide|Boron|11}}'''
|-id=Beryllium-12m
| style="text-indent:1em" | {{SimpleNuclide|Beryllium|12|m}}
| colspan="3" style="text-indent:2em" | {{val|2251|(1)|u=keV}}
| {{val|233|(7)|u=ns}}
| [[Nuclear isomer#Decay processes|IT]]
| {{SimpleNuclide|Beryllium|12}}
| 0+
|
|-id=Beryllium-13
| {{SimpleNuclide|Beryllium|13}}
|4
|9
| {{val|13.036135|(11)}}
| {{val|1.0|(7)|u=zs}}
| [[neutron emission|n]] ?<ref group="n" name="decay mode 1" />
| {{SimpleNuclide|Beryllium|12}} ?
| (1/2−)
|
|-id=Beryllium-13m
| style="text-indent:1em" | {{SimpleNuclide|Beryllium|13|m}}
| colspan="3" style="text-indent:2em" | {{val|1500|(50)|u=keV}}
| 
| 
| 
| (5/2+)
|
|-id=Beryllium-14
| rowspan=5|{{SimpleNuclide|Beryllium|14}}<ref group="n">Has 4 halo neutrons</ref>
| rowspan=5|4
| rowspan=5|10
| rowspan=5|{{val|14.04289|(14)}}
| rowspan=5|{{val|4.53|(27)|u=ms}}
| β<sup>−</sup>n ({{val|86|(6)|u=%}})
| {{SimpleNuclide|Boron|13}}
| rowspan=5|0+
| rowspan=5|
|-
| β<sup>−</sup> (> {{val|9.0|(6.3)|u=%}})
| {{SimpleNuclide|Boron|14}}
|-
| β<sup>−</sup>2n ({{val|5|(2)|u=%}})
| {{SimpleNuclide|Boron|12}}
|-
| β<sup>−</sup>t ({{val|0.02|(1)|u=%}})
| {{SimpleNuclide|Beryllium|11}}
|-
| β<sup>−</sup>α (< {{val|0.004|u=%}})
| {{SimpleNuclide|Lithium|10}}
|-id=Beryllium-14m
| style="text-indent:1em" | {{SimpleNuclide|Beryllium|14|m}}
| colspan="3" style="text-indent:2em" | {{val|1520|(150)|u=keV}}
| 
| 
| 
| (2+)
|
|-id=Beryllium-15
| {{SimpleNuclide|Beryllium|15}}
|4
|11
| {{val|15.05349|(18)}}
| {{val|790|(270)|u=ys}}
| n
| {{SimpleNuclide|Beryllium|14}}
| (5/2+)
|
|-id=Beryllium-16
| {{SimpleNuclide|Beryllium|16}}
|4
|12
| {{val|16.06167|(18)}}
| {{val|650|(130)|u=ys}}<br/>[{{val|0.73|(18)|u=MeV}}]
|2n
|{{SimpleNuclide|Beryllium|14}}
| 0+
|
{{Isotopes table/footer}}

==Beryllium-7==
Beryllium-7 is an isotope with a half-life of 53.3 days that is generated naturally as a cosmogenic nuclide.<ref name="7Be-Mishra"/> The rate at which the short-lived {{SimpleNuclide|Beryllium|7}} is transferred from the air to the ground is controlled in part by the weather. {{SimpleNuclide|Beryllium|7}} decay in the Sun is one of the sources of [[solar neutrino]]s, and the first type ever detected using the [[Homestake experiment]]. Presence of {{SimpleNuclide|Beryllium|7}} in sediments is often used to establish that they are fresh, i.e. less than about 3–4 months in age, or about two half-lives of {{SimpleNuclide|Beryllium|7}}.<ref name="yamamoto">{{cite journal |last1=Yamamoto |first1=Masayoshi |last2=Sakaguchi |first2=Aya |last3=Sasaki |first3=Keiichi |last4=Hirose |first4=Katsumi |last5=Igarashi |first5=Yasuhito |last6=Kim |first6=Chang Kyu |title=Seasonal and spatial variation of atmospheric 210Pb and 7Be deposition: features of the Japan Sea side of Japan |journal=Journal of Environmental Radioactivity |date=January 2006 |volume=86 |issue=1 |pages=110–131 |doi=10.1016/j.jenvrad.2005.08.001|pmid=16181712 }}</ref>

[[File:Be7fromcosmicrays.png|center|thumb|500px|The rate of delivery of {{SimpleNuclide|Beryllium|7}} from the air to the ground in Japan<ref name="yamamoto"/>]]

==Beryllium-8==
{{main|Beryllium-8}}
Beryllium-8 decays into two [[alpha particle]]s with an extremely short half-life of {{val|8.19|e=-17}} seconds, a consequence of its total ground-state energy being ~92&nbsp;keV greater than that of two alpha particles. This is unusual among light {{nowrap|''N'' {{=}} ''Z''}} nuclides and creates a bottleneck in [[stellar nucleosynthesis]], which must be bypassed by the [[triple-alpha process|fusion of three alpha particles]] to form stable [[carbon-12]].

==Beryllium-10==
{{main|Beryllium-10}}

[[Image:Solar Activity Proxies.png|thumb|right|upright=1|Plot showing variations in solar activity, including variation in <sup>10</sup>Be concentration which varies inversely with solar activity. (Note that the beryllium scale is inverted, so increases on this scale indicate lower beryllium-10 levels).]]

Beryllium-10 has a half-life of {{val|1.39e6|u=y}}, and decays by [[beta decay]] to stable [[boron-10]] with a maximum energy of 556.2 keV.<ref name="Korschinek">{{cite journal|author1=G. Korschinek|author2=A. Bergmaier|author3=T. Faestermann|author4=U. C. Gerstmann|journal=Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms| volume=268|issue=2|  year=2010| pages=187–191|title=A new value for the half-life of <sup>10</sup>Be by Heavy-Ion Elastic Recoil Detection and liquid scintillation counting|doi=10.1016/j.nimb.2009.09.020|bibcode=2010NIMPB.268..187K}}</ref><ref name="Chmeleff">{{cite journal|author1=J. Chmeleff|author2=F. von Blanckenburg|author3=K. Kossert|author4=D. Jakob|journal=Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms| volume=268|issue=2| year=2010| pages=192–199|title=Determination of the <sup>10</sup>Be half-life by multicollector ICP-MS and liquid scintillation counting|  doi=10.1016/j.nimb.2009.09.012|bibcode=2010NIMPB.268..192C|url=http://gfzpublic.gfz-potsdam.de/pubman/item/escidoc:239521}}</ref> It is formed in the Earth's atmosphere mainly by [[cosmic ray spallation]] of nitrogen and oxygen.<ref name="Kov10">{{cite journal|author1=G.A. Kovaltsov|author2=I.G. Usoskin|journal=Earth Planet. Sci. Lett.| volume=291|issue=1–4| year=2010| pages=182–199|title=A new 3D numerical model of cosmogenic nuclide <sup>10</sup>Be production in the atmosphere|doi=10.1016/j.epsl.2010.01.011|bibcode=2010E&PSL.291..182K}}</ref><ref name="Beer12">{{cite book|author1=J. Beer|author2=K. McCracken|author3 = R. von Steiger|year=2012|publisher = Physics of Earth and Space Environments, Springer, Berlin |title=Cosmogenic radionuclides: theory and applications in the terrestrial and space environments| volume= 26| doi=10.1007/978-3-642-14651-0|series=Physics of Earth and Space Environments|isbn=978-3-642-14650-3|s2cid=55739885}}</ref><ref name="Pol16">{{cite journal|author1=S.V. Poluianov|author2=G.A. Kovaltsov|author3=A.L. Mishev|author4=I.G. Usoskin|journal=J. Geophys. Res. Atmos.| volume=121|issue=13| year=2016| pages=8125–8136|title= Production of cosmogenic isotopes <sup>7</sup>Be, <sup>10</sup>Be, <sup>14</sup>C, <sup>22</sup>Na, and <sup>36</sup>Cl in the atmosphere: Altitudinal profiles of yield functions|doi=10.1002/2016JD025034|arxiv=1606.05899|bibcode=2016JGRD..121.8125P|s2cid=119301845}}</ref> <sup>10</sup>Be and its daughter product have been used to examine [[soil erosion]], [[soil formation]] from [[regolith]], the development of [[laterite|lateritic soils]] and the age of [[ice core]]s.<ref name="BalcoShuster2009">{{cite journal|last1= Balco|first1= Greg|last2= Shuster|first2= David L.|year= 2009|title= <sup>26</sup>Al-<sup>10</sup>Be–<sup>21</sup>Ne burial dating|journal= [[Earth and Planetary Science Letters]]|volume= 286|issue= 3–4|pages= 570–575|doi= 10.1016/j.epsl.2009.07.025|url= http://www.bgc.org/shuster/BalcoShuster(2009b)_Al_Be_Ne_burial_dating.pdf|bibcode= 2009E&PSL.286..570B|access-date= 2012-12-10|archive-date= 2015-09-23|archive-url= https://web.archive.org/web/20150923184215/http://www.bgc.org/shuster/BalcoShuster(2009b)_Al_Be_Ne_burial_dating.pdf|url-status= dead}}</ref> <sup>10</sup>Be is a significant isotope used as a [[proxy data]] measure for cosmogenic nuclides to characterize solar and extra-solar attributes of the past from terrestrial samples.<ref name="Paleari">{{cite journal  | last = Paleari  | first = Chiara I.  | author2 = F. Mekhaldi  |author3 = F. Adolphi  |author4 = M. Christl  |author5 = C. Vockenhuber  |author6 = P. Gautschi  |author7 = J. Beer  |author8 = N. Brehm  |author9 = T. Erhardt  |author10 = H.-A. Synal  |author11 = L. Wacker  |author12 = F. Wilhelms  |author13 = R. Muscheler  | title = Cosmogenic radionuclides reveal an extreme solar particle storm near a solar minimum 9125 years BP  | journal = Nat. Commun.  | volume = 13  | issue = 214  | date = 2022  | page = 214 | doi = 10.1038/s41467-021-27891-4 | pmid = 35017519 | pmc = 8752676 | bibcode = 2022NatCo..13..214P |doi-access = free  }}</ref>

==Decay chains==
Most isotopes of beryllium within the proton/neutron [[nuclear drip line|drip&nbsp;line]]s decay via [[beta decay]] and/or a combination of beta decay and [[alpha decay]] or neutron emission. However, {{SimpleNuclide|Beryllium|7}} decays only via [[electron capture]], a phenomenon to which its unusually long half-life may be attributed. Notably, its half-life can be artificially lowered by 0.83% via [[Endohedral fullerene|endohedral]] enclosure (<sup>7</sup>Be@C<sub>60</sub>).<ref>{{cite journal |last1=Ohtsuki |first1=T. |last2=Yuki |first2=H. |last3=Muto |first3=M. |last4=Kasagi |first4=J. |last5=Ohno |first5=K. |title=Enhanced Electron-Capture Decay Rate of 7Be Encapsulated in C60 Cages |journal=Physical Review Letters |date=9 September 2004 |volume=93 |issue=11 |pages=112501 |doi=10.1103/PhysRevLett.93.112501 |pmid=15447332 |bibcode=2004PhRvL..93k2501O |url=https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.93.112501 |access-date=23 February 2022|url-access=subscription }}</ref> Also anomalous is {{SimpleNuclide|Beryllium|8}}, which decays via alpha decay to {{SimpleNuclide|Helium|4}}. This alpha decay is often considered fission, which would be able to account for its extremely short half-life.
:<math chem>\begin{array}{l}{}\\
\ce{^6_4Be -> [5 \ \ce{zs}] {^4_2He} + {2^1_1H}} \\
\ce{{^7_4Be} + e^- -> [53.22 \ \ce{d}] {^7_3Li}} \\
\ce{^8_4Be -> [81.9 \ \ce{as}] {2^4_2He}} \\
\ce{^{10}_4Be -> [1.387 \ \ce{Ma}] {^{10}_5B} + e^-} \\
\ce{^{11}_4Be -> [13.76 \ \ce{s}] {^{11}_5B} + e^-} \\
\ce{^{11}_4Be -> [13.76 \ \ce{s}] {^7_3Li} + {^4_2He} + e^-} \\
\ce{^{12}_4Be -> [21.46 \ \ce{ms}] {^{12}_5B} + e^-} \\
\ce{^{12}_4Be -> [21.46 \ \ce{ms}] {^{11}_5B} + {^1_0n} + e^-} \\
\ce{^{13}_4Be -> [1 \ \ce{zs}] {^{12}_4Be} + {^1_0n}} \\
\ce{^{14}_4Be -> [4.53 \ \ce{ms}] {^{13}_5B} + {^1_0n} + e^-} \\
\ce{^{14}_4Be -> [4.53 \ \ce{ms}] {^{14}_5B} + e^-} \\
\ce{^{14}_4Be -> [4.53 \ \ce{ms}] {^{12}_5B} + {2^1_0n} + e^-} \\
\ce{^{15}_4Be -> [790 \ \ce{ys}] {^{14}_4Be} + {^1_0n}} \\{}
\ce{^{16}_4Be -> [650 \ \ce{ys}] {^{14}_4Be} + {2^1_0n}} \\{}
\end{array}</math>

==See also==
'''Daughter products other than beryllium'''
* [[Isotopes of boron]]
* [[Isotopes of lithium]]
* [[Isotopes of helium]]

== Notes ==
{{reflist|group=nb}}

== References ==
{{Reflist}}

{{Navbox element isotopes}}
{{Authority control}}

[[Category:Isotopes of beryllium| ]]
[[Category:Beryllium]]
[[Category:Lists of isotopes by element|Beryllium]]