Isotopes of fluorine

has 19 known isotopes ranging from to and two isomers. Only fluorine-19 is stable and naturally occurring in more than trace quantities; therefore, fluorine is a monoisotopic and a mononuclidic element.
The longest-lived radioisotope is fluorine-18| with a half-life of 109.734 minutes, followed by fluorine-17| with 64.37 seconds. These unstable isotopes participate in the CNO cycle within stars. All other fluorine isotopes have half-lives of less than 12 seconds, and most of those less than 1/2 second.

List of isotopes

Fluorine-18

Of the unstable nuclides of fluorine, has the longest half-life,. It decays to via β⁺ decay. For this reason is a commercially important source of positrons. Its major value is in the production of the radiopharmaceutical fludeoxyglucose, used in positron emission tomography in medicine.
Fluorine-18 is the second lightest unstable nuclide with equal numbers of protons and neutrons and lightest such with an odd atomic number, having 9 of each.

Fluorine-19

Fluorine-19 is the only stable isotope of fluorine. Its abundance is ; no other isotopes of fluorine exist in significant quantities. Its binding energy is. Fluorine-19 is NMR-active with a spin of 1/2+, so it is used in fluorine-19 NMR spectroscopy.

Isomers

Only two nuclear isomers, fluorine-18m and fluorine-26m, have been characterized. The half-life of before it undergoes isomeric transition is. This is less than the decay half-life of any of the particle-bound fluorine radioisotope nuclear ground states. The half-life of is ; it decays mainly to its ground state of or to one of high excited states of with delayed neutron emission.