Isotopes of helium

Helium has two stable isotopes, Helium-3 (\(^3\text{He}\)) and Helium-4 (\(^4\text{He}\)), and one unstable isotope, Helium-5 (\(^5\text{He}\)). 1. **Helium-3 (\(^3\text{He}\))**: This isotope has two protons and one neutron. It is relatively rare, constituting about 0.01% of naturally occurring helium.