Helium Isotopes, Radioactive Decay and Half-Life

This is a periodic table tile for the element helium.
This is a periodic table tile for the element helium. Todd Helmenstine

It takes two protons to make a helium atom. The difference between isotopes is the number of neutrons. Helium has seven known isotopes, ranging from He-3 to He-9. Most of these isotopes have multiple decay schemes where the decay type depends on the overall energy of the nucleus and its total angular momentum quantum number.

This table lists helium isotopes, half-life, and type of decay:

Isotope Half-Life Decay
He-3 Stable N/A
He-4 Stable
≈ 0.5 x 10-21 sec - 1 x 10-21 sec
N/A
p or n
He-5 1 x 10-21 sec n
He-6 0.8 sec
5 x 10-23 sec - 5 x 10-21 sec
β-
n
He-7 3 x 10-22 sec - 4 x 10-21 sec n
He-8 0.1 sec
0.5 x 10-21 sec - 1 x 10-21 sec
β-
n/α
He-9 unknown unknown
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Your Citation
Helmenstine, Anne Marie, Ph.D. "Helium Isotopes, Radioactive Decay and Half-Life." ThoughtCo, Jul. 29, 2021, thoughtco.com/isotopes-of-helium-607735. Helmenstine, Anne Marie, Ph.D. (2021, July 29). Helium Isotopes, Radioactive Decay and Half-Life. Retrieved from https://www.thoughtco.com/isotopes-of-helium-607735 Helmenstine, Anne Marie, Ph.D. "Helium Isotopes, Radioactive Decay and Half-Life." ThoughtCo. https://www.thoughtco.com/isotopes-of-helium-607735 (accessed October 28, 2021).