An unstable atom gives off its excess energy until it becomes stable. The energy emitted is radiation.
不稳定原子在达到稳定状态前，需要释放出自身多余的能量，这一能量即辐射。
2
The process by which an atom changes from an unstable state to a more stable state by emitting radiation is called radioactive decay or radioactivity.
原子通过辐射由不稳定状态转变为更加稳定状态的过程称为放射性衰变或放射性。
3
"What it amounts to, " said Billings, "is that The Goose can convert any radioactive isotope into a stable one. It has developed the perfect defense against radiation sickness.