Science, Tech, Math › Science Is Deuterium Radioactive? Isotopes and Radioactivity Share Flipboard Email Print This is glowing deuterium in an IEC reactor. Although this is a picture of a reactor, the glow is due to the ionization of deuterium, not radioactivity. Benji9072/Wikimedia Commons Science Chemistry Periodic Table Basics Chemical Laws Molecules Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated May 20, 2019 Deuterium is one of the three isotopes of hydrogen. Each deuterium atom contains one proton and one neutron. The most common isotope of hydrogen is protium, which has one proton and no neutrons. The "extra" neutron makes each atom of deuterium heavier than an atom of protium, so deuterium is also known as heavy hydrogen. Although deuterium is an isotope, is not radioactive. Both deuterium and protium are stable isotopes of hydrogen. Ordinary water and heavy water made with deuterium are similarly stable. Tritium is radioactive. It's not always easy to predict whether an isotope will be stable or radioactive. Most of the time, radioactive decay occurs when there is a significant difference between the number of protons and neutrons in an atomic nucleus.