actinium

[ ak-tin-ee-uh m ]

/ ækˈtɪn i əm /

noun Chemistry.

a radioactive silver-white metallic element that glows blue in the dark, resembling the rare earths in chemical behavior and valence. Symbol: Ac; atomic number: 89; atomic weight: 227.

Nearby words

Origin of actinium

First recorded in 1900–05; actin- + -ium

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for actinium

For if actinium was an independent element we would be sure to find actinium haloes.
The Birth-Time of the World and Other Scientific Essays|J. (John) Joly
Actinium, an element or elementary substance obtained in minute quantities in connection with the study of radioactivity.
The New Gresham Encyclopedia. Vol. 1 Part 1|Various
These are generally known as radium emanation, thorium emanation, and actinium emanation.
A Brief Account of Radio-activity|Francis Preston Venable
In this class are now placed also the three radio-active gases, emanating respectively from radium, thorium, and actinium.
A Brief Account of Radio-activity|Francis Preston Venable

Emanium was the name originally proposed by Giesel for the body now known as actinium.
A Brief Account of Radio-activity|Francis Preston Venable

British Dictionary definitions for actinium

actinium

/ (ækˈtɪnɪəm) /

noun

a radioactive element of the actinide series, occurring as a decay product of uranium. It is used as an alpha-particle source and in neutron production. Symbol: Ac; atomic no: 89; half-life of most stable isotope, 227 Ac: 21.6 years; relative density: 10.07; melting pt: 1051°C; boiling pt: 3200 ± 300°C

Word Origin for actinium

C19: New Latin, from actino- + -ium

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for actinium

actinium

radioactive element discovered in 1899, from Greek actin-, comb. form of aktis (genitive aktinos) "ray, radiance" (see actino-) + chemical suffix -ium.

Medicine definitions for actinium

actinium

[ ăk-tĭn′ē-əm ]

n. Symbol Ac

A radioactive element found in uranium ores. Its longest lived isotope is Ac 227 with a half-life of 21.6 years. Atomic number 89.

Science definitions for actinium

actinium

[ ăk-tĭn′ē-əm ]

Ac

A silvery-white, highly radioactive metallic element of the actinide series that is found in uranium ores. It is about 150 times more radioactive than radium and is used as a source of alpha rays and neutrons. Its most stable isotope has a half-life of about 22 years. Atomic number 89; melting point 1,050°C (1,922°F); boiling point (estimated) 3,200°C (5,792°F); specific gravity (calculated) 10.07; valence 3. See Periodic Table.