There is no single chemical formula for radioactive, as radioactivity is not a property of a specific chemical element or compound. Rather, radioactivity refers to the process by which certain unstable atomic nuclei lose energy by emitting radiation in the form of particles or electromagnetic waves.

Radioactivity can occur naturally in certain isotopes of elements, such as uranium, plutonium, and radium, which have unstable atomic nuclei and undergo radioactive decay over time.

Commonly known radioactive elements and their chemical symbols are:

- Uranium (U)

- Plutonium (Pu)

- Radium (Ra)

- Polonium (Po)

- Thorium (Th)

- Americium (Am)

- Curium (Cm)

- Fermium (Fm)

- Einsteinium (Es)

- Mendelevium (Md)