An isotope undergoes radioactive decay. The new isotope that forms has an atomic number that is 2 less than the original isotope’s. Which kind of decay has occurred, and how do you know?

Alpha decay emits an alpha particle, which contains two protons and two neutrons. Losing its two protons makes the original atom’s atomic number decrease by 2, matching the new isotope. Beta decay changes the atomic number by 1, while gamma decay does not change it. The correct choice is C, alpha decay because alpha particles have two protons and two neutrons.

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