Germanium-73

Main isotopes of germanium

iso NA half-life DM DE (MeV) DP 68Ge syn 270.8 d ε – 68Ga 70Ge 20.52% is stable with 38 neutrons 71Ge syn 11.3 d ε – 71Ga 72Ge 27.45% is stable with 40 neutrons 73Ge 7.76% is stable with 41 neutrons 74Ge 36.52% is stable with 42 neutrons 76Ge 7.75% 1.78×1021 y β−β− 2.039 76Se
Standard atomic weight (Ar)	72.630(8)

Germanium (₃₂Ge) has five naturally occurring isotopes, ⁷⁰Ge, ⁷²Ge, ⁷³Ge, ⁷⁴Ge, and ⁷⁶Ge. Of these, ⁷⁶Ge is very slightly radioactive, decaying by double beta decay with a half-life of 1.78 × 10²¹ years (130 billion times the age of the universe).

Stable ⁷⁴Ge is the most common isotope, having a natural abundance of approximately 36%. ⁷⁶Ge is the least common with a natural abundance of approximately 7%. When bombarded with alpha particles, the isotopes ⁷²Ge and ⁷⁶Ge will generate stable ⁷⁵As and ⁷⁷Se, releasing high energy electrons in the process.

At least 27 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 270.95 d. It decays to the medically useful positron-emitting isotope ⁶⁸Ga. (See gallium-68 generator for notes on the source of this isotope, and its medical use). The least stable known germanium isotope is ⁶⁰Ge with a half-life of 30 ms.

While most of germanium's radioisotopes decay by beta decay, ⁶¹Ge and ⁶⁴Ge decay by β⁺ delayed proton emission.⁸⁴Ge through ⁸⁷Ge also have minor β⁻ delayed neutron emission decay paths.

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