Some elements of atomic nuclei are unstable because of the presence of excess nuclear charge inside it so these nuclei undergo radioactive decay to form stable nuclei. These elements are called radioactive elements.
Radioactivity - The emission of radiation from an atom with an unstable nucleus, is a chemical property.
On the periodic table of elements, the elements that have no stable isotopes are considered radioactive.
Radioactive decay is a property of several naturally occurring elements as well as of artificially produced isotopes of the elements.
Learn more about radioactive elements here:
