How many stable isotopes of He exist?

1 Answer
May 5, 2014

There are two stable isotopes of helium.


There are nine known isotopes of helium.

They range from helium-2 to helium-10.

Only helium-3 and helium-4 are stable.

All the radioisotopes are short-lived.

The longest-lived is helium-6, with a half-life of 810 ms.

The least stable isotope is helium-5, with a half-life of 7.6×10⁻²² s.

Helium-2 may have an even shorter half-life.