Why are some elements radioactive?
Quick Answer
Some elements are radioactive because their atomic nuclei are unstable and spontaneously break down into more stable forms. This happens when the balance of protons and neutrons cannot hold the nucleus together well enough.
The Full Story
A radioactive element has an unstable nucleus that changes over time by emitting particles or energy. This may happen because the nucleus is too large, has an imbalanced proton-to-neutron ratio, or has too much internal energy. Heavy elements such as uranium and radium are well-known for radioactive decay, but some lighter isotopes are radioactive too. The process can produce alpha, beta, or gamma radiation and may transform one element into another.
Key Facts
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"Why do some atoms literally fall apart on their own?"