Isotopes of beryllium
has 11 known isotopes and 3 known isomers, but only one of these isotopes 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. Beryllium is unique as being the only monoisotopic element with an even number of protons and also has an odd number of neutrons; the 25 other monoisotopic elements all have odd numbers of protons, and even of neutrons, so the total mass number is still odd.
Of the 10 radioisotopes of beryllium, the most stable are with a half-life of 1.387 million years and with a half-life of 53.22 days. All other radioisotopes have half-lives shorter than 15 seconds.
The 1:1 neutron–proton ratio seen in stable isotopes of many light elements is prevented in beryllium by the extreme instability of toward splitting into two nuclei, which may be seen either alpha decay or a type of fission; in any case the half-life is only, short enough to normally be considered unbound. This, as with the relative instability of all lithium, beryllium, and boron isotopes, is favored due to the extremely tight binding of the helium-4 nucleus.
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, has a half-life above a million years and a decay energy less than 1 MeV, which indicates unusual stability given that condition.
Most beryllium present 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 and are both cosmogenic nuclides because they are made, in the Solar System, continually at the rate they decay by spallation, as is carbon-14.
List of isotopes
Beryllium-7
Beryllium-7 is an isotope with a half-life of 53.22 days that is generated naturally as a cosmogenic nuclide. It is also a nuisance byproduct in nuclear reactors and accelerators. 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 neutrinos, and the first type ever detected using the Homestake experiment. 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.Beryllium-8
Beryllium-8 decays immediately into two alpha particles as its total energy is about 92 keV greater than that of the two alpha particles, and the Coulomb barrier to decay is negligible. This is unusual among light nuclides and creates a bottleneck in stellar nucleosynthesis, which requires that a third alpha be immediately captured, known as the fusion of three alpha particles, to form stable carbon-12 and thence all heavier elements.Beryllium-10
Beryllium-10 has a half-life of 1.387 million years and beta decays to stable Boron-10 with a maximum energy of 556.0 keV:Beryllium-10 is formed in the Earth's atmosphere mainly by cosmic ray spallation of nitrogen and oxygen.
Because beryllium tends to exist in solutions below about pH 5.5, it will dissolve and be transported to the Earth's surface via rainwater. As the precipitation quickly becomes more alkaline, beryllium drops out of solution. Cosmogenic 10Be thereby accumulates at the soil surface, where its relatively long half-life does not limit its residence time there.
10Be and its daughter product have been used in surface exposure dating to examine soil erosion, soil formation from regolith, the development of lateritic soils and the age of ice cores. It is also formed in nuclear explosions by a reaction of fast neutrons with 13C in the carbon dioxide in air, and is one of the historical indicators of past activity at nuclear test sites. 10Be decay 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.
The rate of production of beryllium-10 depends on the activity of the sun. When solar activity is low, the barrier against cosmic rays that exists beyond the termination shock is weakened. This means more beryllium-10 is produced, and it can be detected millennia later. Beryllium-10 can thus serve as a marker of Miyake events, such as the 774–775 carbon-14 spike. There can be an effect on climate. While other cosmogenic isotopes experience similar cycles, the high rate of production, long half-life, and relative immobility in the environment make this most suitable for this purpose.