Radioactive elements are mostly found toward the bottom of the periodic table, especially among the heaviest elements with large atomic numbers.

Quick Scoop

  • Many elements with atomic number greater than about 82–84 (like uranium, plutonium, and beyond) are inherently unstable and thus radioactive.
  • These heavy radioactive elements occupy the bottom rows , including:
    • The actinides (elements 89–103), which are all radioactive.
* The artificial “superheavy” elements from roughly 104 to 118, which are all short‑lived and radioactive.
  • There are also a few lighter elements that are entirely radioactive (for example technetium, element 43, and promethium, element 61), but they are exceptions scattered in the middle of the table.

So, while radioactive isotopes can exist all over the table, the elements that have no stable isotopes at all tend to cluster in the lower part of the periodic table, especially among the actinides and the superheavy elements.

Information gathered from public forums or data available on the internet and portrayed here.