Oganesson, with an atomic number of 118, holds the title for being the most radioactive element in the known universe. Its extreme radioactivity arises from several factors:

Extremely Unstable Nucleus:

The atomic nuclei of heavier elements, like Oganesson, are exceptionally unstable due to the high number of protons crammed together within a tiny space. This instability drives the radioactive decay processes observed in these elements.

Short Half-Life:

Oganesson's most stable isotope, Og-294, has a half-life of approximately 0.89 milliseconds. Its other isotopes have even shorter half-lives. This means that the element undergoes rapid radioactive decay, releasing copious amounts of radiation in a short time span.

Multiple Decay Modes:

Oganesson exhibits various radioactive decay modes, including alpha decay, beta decay, and spontaneous fission. Alpha and beta decays involve the emission of alpha and beta particles, respectively, while spontaneous fission results in the splitting of the nucleus into smaller nuclei. These decay processes contribute to the element's high radioactivity.

High Decay Energy:

The decay processes of Oganesson are accompanied by the release of substantial energy. The energy released during these decays can be measured in millions of electron volts (MeV), making Oganesson not only highly radioactive but also a source of significant radiation energy.

Limited Production and Accessibility:

Oganesson is extremely rare and challenging to produce. Scientists use particle accelerators to synthesize heavier elements, including Oganesson, by fusing atomic nuclei. Due to its short-lived nature, Oganesson atoms exist for only a fraction of a second before undergoing decay. This limited availability further contributes to its uniqueness and its designation as the most radioactive element.