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.

QUIZZES

DO YOU KNOW THIS VOCABULARY FROM "THE HANDMAID'S TALE"?

"The Handmaid's Tale" was required reading for many of us in school. Everyone else has probably watched the very popular and addictive TV show. Do you remember this vocabulary from the book, and do you know what these terms mean?
Question 1 of 10
decorum
the act of or need for making up one's mind.
dignified propriety of behavior, speech, dress, etc.
a company of singers, especially an organized group employed in church service.
TAKE THE QUIZ TO FIND OUT

Origin of actinium

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

Words nearby actinium

actinide, actinide series, actiniform, actinin, actinism, actinium, actinium series, actino-, actinobacillosis, actinobacillus, actinobiology
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for actinium

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

Medical 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.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific 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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.