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Name: Lee
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i have read somewhere that tellurium is the lightest element that can undergo alpha decay. But i have read that beryllium-8 can undergo alpha decay. Which is true?


When an unstable isotope undergoes alpha decay the nucleus gives up two neutrons and two protons. This type of decay will define the atom with the lowest atomic number that can undergo alpha decay.

You are correct: several of the lower mass isotopes of tellurium do undergo alpha decay; beryllium-8 also undergoes alpha decay.

Yet, beryllium-6 undergoes alpha decay, lithium-5 undergoes alpha decay, and helium-5 undergoes alpha decay. Hydrogen has only one proton, therefore none of the isotopes of hydrogen can undergo alpha decay. It looks like helium-5 is the winner of your contest.

Take a look at the Nuclear Wallet Cards from the National Nuclear Data Center of the Brookhaven National Laboratories at


Leslie Kanat, Ph.D.
Professor of Geology
Department of Environmental Sciences
Johnson State College

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