Untriennium

Untriennium (pronounced /ʌntraɪˈɛniəm/, also called eka-actinium or dvi-lanthanum) is an unsynthesized chemical element with atomic number 139 and symbol Ute.

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The name untriennium is a temporary IUPAC systematic element name.

History

The name untriennium is used as a placeholder, as in scientific articles about the search for element 139. Transuranic elements (those beyond uranium) are, except for microscopic quantities and except for plutonium, always artificially produced, and usually end up being named for a scientist or the location of a laboratory that does work in atomic physics (see systematic element name for more information).

Significance

In a non-relativistic approximation, the speed of an electron in a 1s electron orbital, v, is estimated to approach the speed of light for 1s orbitals in element 138. At element 139, it is predicted that these electrons will have a speed in excess of c and as such would not have stable electron orbitals.

It is the first element with a filled type G electron shell, holding 18 electrons, and an electron in the overlaying type F orbital, in its ground state.

See also

• Lanthanum
• Dvi-Lanthanum — Dvi-Cerium
• Actinium
• Eka-Radium — Eka-Actinium — Eka-Thorium
• Eka-Seaborgium — Eka-Bohrium — Eka-Hassium
• Untrioctium