n. Symbol Es A synthetic transuranic element first produced by neutron irradiation of uranium in a thermonuclear explosion and now usually produced in the laboratory by irradiating plutonium and other elements. The isotopes with the longest half-lives are Es-252 (472 days) and Es-254 (276 days). Atomic number 99; melting point 860°C (estimated); valence 2, 3. See Periodic Table. [After Albert Einstein.] |
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.