Unknown

The transactinide elements all have electrons in the 6d subshell in their ground state. These elements are very radioactive with extremely short half-lives of minutes or less. Furthermore, they have been only obtained synthetically in laboratories. None of these elements have ever been collected in a microscopic sample. Isotopes of these elements are radioactive in usual way: they decay by emitting alpha particles, beta particles and gamma rays and they also fission spontaneously. All of these elements are named after physicists or chemists or important locations involved in the synthesis of the elements. The transactinides synthesized in four laboratories from 1964 to 2013 – the Lawrence Berkeley National Laboratory in the USA, the joint Institute for Nuclear Research in Russia, the GSI Helmholtz Center for Heavy Ion Research in Germany and RIKEN in Japan. These discoveries completed the seventh period of the periodic table. The remaining two transactinides with atomic numbers 119 and 120 have not yet been synthesized. They would begin the eighth period.

The synthesis of these elements thorough nuclear reactions has been an important source of knowledge about them. The knowledge has expanded scientific understanding of the fundamental structure of matter and makes it possible to predict the existence and basic properties of elements much heavier than any currently known. Present theory suggests that the maximum atomic number could be found to lie somewhere between 170 and 210, if nuclear instability would not preclude the existence of such elements. Although the decay properties of these elements, as well as the transuranium elements, are important with regard to the potential application of the elements, these elements have been studied largely to develop a fundamental understanding of nuclear reaction and nuclear and atomic structure.

Since only small amounts of these elements have ever been produced, they currently have no uses outside of basic scientific research.

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