Question

How does radioactive decay work?

Answer 1

When a nucleus is unstable, it can release mass and energy in radioactive decay to become stable.

Explanation:

Radioactive decay is when the nucleus of an atom is unstable (has an imbalance of protons and neutrons) and so releases particles of various sorts to become stable.

Stable and unstable combinations of neutrons and protons are shown on the band of stability graph,

which graphs number of protons against number of neutrons and shows where the stable nuclei are. Anything outside of this band will decay, release mass and energy, to become stable and inside the band.

If a nucleus is simply too big, it can undergo `alpha`-decay, where two protons and two neutrons are released as a helium-nucleus. This decreases the overall mass by `4` and the atomic number by `2`, making a new element entirely.

If it has too many neutrons, it undergoes `beta`-decay, where a neutron decays into a proton. Because they weigh roughly the same, the mass number doesn't change, but the atomic number increases by `1`, again making a new element.

Normally after `alpha` or `beta`-decay, a nucleus is left in an excited state, where it has too much energy. This is released in `gamma`-decay, which is a photon (light-particle) in the `gamma` area of the electromagnetic spectrum.