transactinide element

American

[trans-ak-tuh-nahyd, tranz-] / trænsˈæk təˌnaɪd, trænz- /

noun

Chemistry, Physics.

any element having an atomic number higher than 103, the last of the actinide series. These superheavy, radioactive elements are extremely short-lived, and can only be created in the laboratory.

First recorded in 1965–70; trans- + actinide

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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023