Isotopes of germanium

Germanium (₃₂Ge) has five naturally occurring isotopes, ⁷⁰Ge, ⁷²Ge, ⁷³Ge, ⁷⁴Ge, and ⁷⁶Ge. Of these, ⁷⁶Ge is very slightly radioactive, undergoing double beta decay with a half-life of 2.02 × 10²¹ years (over 100 billion times the age of the universe).

Stable ⁷⁴Ge is the most common isotope, having a natural abundance of 36.52%; ⁷⁶Ge is the least common with a natural abundance of 7.75%.

At least 27 additional radioisotopes have also been synthesized ranging in atomic mass from 58 to 89. The most stable of these is ⁶⁸Ge, decaying by electron capture with a half-life of 271.05 days, whose daughter is the medically useful positron-emitting isotope ⁶⁸Ga. (See gallium-68 generator for notes on the source of this isotope, and its medical use.) The next after that is ⁷¹Ge, also decaying by electron capture with half-life 11.468 days, and the rest are all less than two days, most under two hours.

While most of germanium's radioisotopes decay by beta decay - β⁺ for isotopes lighter than 74-76, and β^- for those heavier - isotopes as heavy as ⁶⁵Ge can also decay by β⁺-delayed proton emission, and those as light as ⁸⁴Ge by β⁻-delayed neutron emission.

⁷⁶Ge is used in experiments on the nature of neutrinos, by searching for neutrinoless double beta decay.

Daughter products other than germanium