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.

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

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

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.

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.