Argon-39 (Ar-39)

Identity

Protons

18

Neutrons

21

Mass number

39

Mass

39.0 ± 5.4 u

Mass excess

-33.242 MeV

Spin

7/2-*

Stability

Half-life: 268 years

Natural occurrence

Not found in nature

Decays to

• beta minus → K-39