Beryllium Beryllium is a chemical element; it has Symbol (chemistry), symbol Be and atomic number 4. It is a steel-gray, hard, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with ...

(₄Be) has 11 known

isotopes Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They 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), but ...

and 3 known

isomers In chemistry, isomers are molecules or polyatomic ions with identical molecular formula – that is, the same number of atoms of each element – but distinct arrangements of atoms in space. ''Isomerism'' refers to the existence or possibili ...

, but only one of these isotopes () is stable and a

primordial nuclide In geochemistry, geophysics and nuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed. Primordial nuclides were present in the ...

. As such, beryllium is considered a

monoisotopic element A monoisotopic element is an element which has only a single stable isotope (nuclide). There are 26 such elements, as listed. Stability is experimentally defined for chemical elements, as there are a number of stable nuclides with atomic number ...

. It is also a

mononuclidic element A mononuclidic element or monotopic element is one of the 21 chemical elements that is found naturally on Earth essentially as a single nuclide (which may, or may not, be a stable nuclide). This single nuclide will have a characteristic atomic ...

, because its other isotopes have such short half-lives that none are primordial and their abundance is very low (

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 ). Beryllium is unique as being the only monoisotopic element with both an even number of

proton A proton is a stable subatomic particle, symbol , Hydron (chemistry), H+, or 1H+ with a positive electric charge of +1 ''e'' (elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an e ...

s and an odd number of

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

s. There are 25 other monoisotopic elements but all have odd atomic numbers, and even numbers of neutrons. Of the 10

radioisotopes A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...

of beryllium, the most stable are with a half-life of million years and with a half-life of . All other radioisotopes have half-lives under , most under . The least stable isotope is , with a half-life of . The 1:1

neutron–proton ratio The neutron–proton ratio (N/Z ratio or nuclear ratio) of an atomic nucleus is the ratio of its number of neutrons to its number of protons. Among stable nuclei and naturally occurring nuclei, this ratio generally increases with increasing atomi ...

seen in stable isotopes of many light elements (up to

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

, and in elements with even atomic number up to

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

) is prevented in beryllium by the extreme instability of toward

alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). The parent nucleus transforms or "decays" into a daughter product, with a mass number that is reduced by four and an a ...

, which is favored due to the extremely tight binding of nuclei. The half-life for the decay of is only . 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, , has a half-life of million years, 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 in the universe is thought to be formed by cosmic ray nucleosynthesis from

cosmic ray spallation Cosmic ray spallation, also known as the x-process, is a set of naturally occurring nuclear reactions causing nucleosynthesis; it refers to the formation of chemical elements from the impact of cosmic rays on an object. Cosmic rays are highly ene ...

in the period between the

Big Bang The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including th ...

and the formation of the Solar System. The isotopes , with a half-life of , and are both

cosmogenic nuclide Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a high-energy cosmic ray interacts with the nucleus of an '' in situ'' Solar System atom, causing nucleons (protons and neutrons) to be expelled from the atom ...

s because they are made on a recent timescale in the Solar System by spallation, like .

List of isotopes

, -id=Beryllium-6 , , 4 , 2 , ,
[] , proton emission, 2p , , 0+ , , - , Produced in Big Bang nucleosynthesis, but not primordial, as it all quickly decayed to ⁷Li , 4 , 3 , , , Electron capture, ε , , 3/2− , Trace

cosmogenic Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a high-energy cosmic ray interacts with the nucleus of an ''in situ'' Solar System atom, causing nucleons (protons and neutrons) to be expelled from the atom ( ...

nuclide , - , Intermediate product of

triple alpha process The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon. In stars Helium accumulates in the cores of stars as a result of the proton–proton chain reaction a ...

stellar nucleosynthesis In astrophysics, stellar nucleosynthesis is the creation of chemical elements by nuclear fusion reactions within stars. Stellar nucleosynthesis has occurred since the original creation of hydrogen, helium and lithium during the Big Bang. As a ...

as part of the path producing ¹²C , 4 , 4 , ,
[] , αAlso often considered spontaneous fission, as splits into two equal nuclei , , 0+ , , -id=Beryllium-8m , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , , , α , , 2+ , , -id=Beryllium-9 , , 4 , 5 , , colspan=3 align=center, Stable , 3/2− , 1 , -id=Beryllium-9m , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , ,
[] , , , 3/2− , , - , Beryllium-10, , 4 , 6 , , , Beta decay, β⁻ , , 0+ , Trace , -id=Beryllium-11 , rowspan=3, Has 1 halo nucleus, halo neutron , rowspan=3, 4 , rowspan=3, 7 , rowspan=3, , rowspan=3, , β⁻ () , , rowspan=3, 1/2+ , rowspan=3, , - , Alpha decay, β⁻α () , , - , β⁻p () , , -id=Beryllium-11m , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , ,
[] , IT ?Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide. , ? , 3/2− , , -id=Beryllium-12 , rowspan=2, , rowspan=2, 4 , rowspan=2, 8 , rowspan=2, , rowspan=2, , β⁻ () , , rowspan=2, 0+ , rowspan=2, , - , β⁻n () , , -id=Beryllium-12m , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , , , IT , , 0+ , , -id=Beryllium-13 , , 4 , 9 , , , n ? , ? , (1/2−) , , -id=Beryllium-13m , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , , , , , (5/2+) , , -id=Beryllium-14 , rowspan=5, Has 4 halo neutrons , rowspan=5, 4 , rowspan=5, 10 , rowspan=5, , rowspan=5, , β⁻n () , , rowspan=5, 0+ , rowspan=5, , - , β⁻ (> ) , , - , β⁻2n () , , - , β⁻t () , , - , β⁻α (< ) , , -id=Beryllium-14m , style="text-indent:1em" , , colspan="3" style="text-indent:2em" , , , , , (2+) , , -id=Beryllium-15 , , 4 , 11 , , , n , , (5/2+) , , -id=Beryllium-16 , , 4 , 12 , ,
[] , 2n , , 0+ ,

Beryllium-7

Beryllium-7 is an isotope with a half-life of 53.3 days that is generated naturally as a cosmogenic nuclide. The rate at which the short-lived is transferred from the air to the ground is controlled in part by the weather. decay in the Sun is one of the sources of

solar neutrino A solar neutrino is a neutrino originating from nuclear fusion in the Sun's core, and is the most common type of neutrino passing through any source observed on Earth at any particular moment. Neutrinos are elementary particles with extremely smal ...

s, and the first type ever detected using the

Homestake experiment The Homestake experiment (sometimes referred to as the Davis experiment or Solar Neutrino Experiment and in original literature called Brookhaven Solar Neutrino Experiment or Brookhaven 37Cl (Chlorine) Experiment) was an experiment headed by astr ...

. Presence of 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 . Be7fromcosmicrays

Beryillum-8

Beryllium-8 decays into two

alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...

s with an extremely short half-life of seconds, a consequence of its total ground-state energy being ~92 keV greater than that of two alpha particles. This is unusual among light nuclides and creates a bottleneck in

, which must be bypassed by the fusion of three alpha particles to form stable

carbon-12 Carbon-12 (12C) is the most abundant of the two stable isotopes of carbon ( carbon-13 being the other), amounting to 98.93% of element carbon on Earth; its abundance is due to the triple-alpha process by which it is created in stars. Carbon-1 ...

Beryllium-10

Beryllium-10 has a half-life of , and decays by

beta decay In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle (fast energetic electron or positron), transforming into an isobar of that nuclide. For example, beta decay of a neutron ...

to stable

boron-10 Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three v ...

with a maximum energy of 556.2 keV. It is formed in the Earth's atmosphere mainly by

of nitrogen and oxygen. ¹⁰Be and its daughter product have been used to examine

soil erosion Soil erosion is the denudation or wearing away of the Topsoil, upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, Atmosphere of Ea ...

soil formation Soil formation, also known as pedogenesis, is the process of soil genesis as regulated by the effects of place, environment, and history. Biogeochemical processes act to both create and destroy order ( anisotropy) within soils. These alteration ...

from

regolith Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestria ...

, the development of lateritic soils and the age of

ice core An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier ...

s. ¹⁰Be is a significant isotope used as a

proxy data In the study of past climates ("paleoclimatology"), climate proxies are preserved physical characteristics of the past that stand in for direct meteorological measurements and enable scientists to reconstruct the climatic conditions over a longe ...

measure for cosmogenic nuclides to characterize solar and extra-solar attributes of the past from terrestrial samples.

Decay chains

Most isotopes of beryllium within the proton/neutron drip lines decay via

and/or a combination of beta decay and

or neutron emission. However, decays only via

electron capture Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Th ...

, 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 enclosure (⁷Be@C₆₀). Also anomalous is , which decays via alpha decay to . This alpha decay is often considered fission, which would be able to account for its extremely short half-life. :

\begin\\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\ce \\
\end

Notes

References

{{Authority control Beryllium