Argon36

Argon-36 is a stable isotope of the element argon (symbol Ar) with mass number 36. It has 18 protons and 18 neutrons, and like many even-even nuclei, its ground-state spin is 0+. It is one of the minor natural isotopes of argon, occurring alongside Ar-38 and Ar-40.

Natural occurrence and abundance

In terrestrial argon, Ar-36 accounts for a small fraction of atoms, typically a few tenths of a percent, with Ar-38 and Ar-40 making up the remainder (Ar-40 is by far the most abundant). Ar-36 is present in Earth's atmosphere as part of the natural argon inventory and can be separated and measured using standard mass spectrometry. Its presence reflects the isotopic composition produced by stellar nucleosynthesis and cosmic-ray interactions over geological timescales.

Stability and decay

Argon-36 is stable and does not undergo radioactive decay under ordinary conditions. Consequently, its quantity in natural argon is not governed by a radioactive half-life.

Properties and applications

As a stable isotope, Ar-36 is primarily of interest in isotope geochemistry and cosmochemistry, where its ratio to other argon isotopes (notably Ar-40 and Ar-38) is used to study atmospheric formation, planetary samples, and calibration of mass spectrometers. Because argon is inert, Ar-36 measurements are typically used to characterize isotopic compositions rather than to serve as a direct dating signal like Ar-39 or Ar-40.

Safety

Argon gas is inert and non-toxic, but as with any compressed gas, it can pose asphyxiation hazards in confined spaces.

See also

Argon, Isotopes of argon, Argon-39, Argon-38, Argon-40.