Radioactive decay

Some combinations are unstable. Such a nucleus can change towards a more stable state by giving out nuclear radiation. This spontaneous change is called radioactive decay.

An unstable nucleus can become more stable by emitting particles or electromagnetic waves. These emissions carry energy away from the nucleus. This process is called radioactive decay, and the emitted particles or waves are called nuclear radiation.

Some nuclei are unstable: they can change spontaneously and give out radiation. This change is called radioactive decay. A particular unstable nucleus might decay soon or much later; we cannot predict exactly when it will happen.

Some combinations of protons and neutrons form unstable nuclei. Such a nucleus may undergo radioactive decay, emitting radiation and changing to a more stable nuclear state. The emission comes from the nucleus, not from the atom's surrounding electron arrangement.