Here's a breakdown:

* Radioactivity is the phenomenon where the nucleus of an atom spontaneously decays, emitting particles and/or energy.

* Atomic particles are the fundamental building blocks of atoms, such as protons, neutrons, and electrons.

* Radioactive elements are elements whose atoms have unstable nuclei, leading them to undergo radioactive decay and emit these particles.

Examples of radioactive elements include:

* Uranium (U)

* Plutonium (Pu)

* Radium (Ra)

* Carbon-14 (C-14)

* Iodine-131 (I-131)