They lose energy and particles and become more stable. As nuclei decay, they gain or lose protons, so the atoms become different elements.

What does a radioactive element lose?

Radioactive decay occurs when an unstable atomic nucleus loses energy by emitting energy in the form of emitted particles or electromagnetic waves, called radiation. Isotopes are atoms of the same element (thereby having the same number of protons) which differ in the number of neutrons in their nucleus.

How do things become radioactive?

When the atoms of an element have extra neutrons or protons it creates extra energy in the nucleus and causes the atom to become unbalanced or unstable. Whether radioactive elements can become stable and if so, how. The unstable nucleus of radioactive atoms emit radiation. This process is called radioactive decay.

Why is Chernobyl still radioactive?

Plutonium-239, extremely radiotoxic when inhaled, has a half life of 24,000 years. Though the main pattern of radioactive fallout—which is blotchy and unpredictable—was established soon after the accident, radioactive particles remain on the move to this day, still shifting on the wind and flowing through the water.