Thus, it is a monoisotopic element.

Cosmogenic 10Be is produced in the atmosphere of the Earth by the cosmic ray spallation of oxygen and nitrogen.

Cosmogenic 10Be accumulates at the soil surface, where its relatively long half-life (1.36 million years) permits a long residence time before decaying to boron-10.

Thus, 10Be and its daughter products are used to examine natural soil erosion, soil formation and the development of lateritic soils, as well as acting as a proxy for measurement of the variations in solar activity and the age of ice cores.

[5]
The production of 10Be is inversely proportional to solar activity, because the increased solar wind during periods of high solar magnetic activity in turn decreases the flux of galactic cosmic rays that reach the Earth.

Nuclear explosions also form 10Be by the reaction of fast neutrons with 13C in the carbon dioxide in air.

This is one of the indicators of past activity at nuclear weapon test sites.

[6]
The isotope 7Be (half life 53 days) is also cosmogenic, and shows an atmospheric abundance linked to sunspots much like 10Be.

8Be has a very short half-life which contributes to its significant cosmological role as elements heavier than beryllium could not have been produced by nuclear fusion in the Big Bang.

[7] This is due to the lack of sufficient time during the Big Bang's nucleosynthesis phase to produce carbon by the fusion of 4He nuclei and the very low concentrations of available beryllium-8.

The British astronomer Sir Fred Hoyle first showed that the energy levels of 8Be and 12C allow carbon production by the so-called triple-alpha process in helium-fueled stars where more nucleosynthesis time is available, thus making carbon-based life possible from the gas and dust ejected by supernovas (see also Big Bang nucleosynthesis).

[8]
Because beryllium's innermost electrons may also be used in chemical bonding, when 7Be decays by electron capture, it does so by taking electrons from atomic orbitals that may participate in bonding.

This makes its decay rate dependent to a measurable degree upon its electron configuration – a rare occurrence in nuclear decay.

[9]
The shortest-lived known isotope of beryllium is 13Be which decays through neutron emission.

It has a half-life of 2.7 × 10−21 second.