actinium

[ ak-tin-ee-uhm ]

noun

, Chemistry.

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

actinium

/ ækˈtɪnɪəm /

noun

1. 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, ²²⁷Ac: 21.6 years; relative density: 10.07; melting pt: 1051°C; boiling pt: 3200 ± 300°C

actinium

/ ăk-tĭn′ē-əm /

1. 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.
2. See Periodic Table

Word History and Origins

Origin of actinium¹

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

Word History and Origins

Origin of actinium¹

C19: New Latin, from actino- + -ium

Example Sentences

Other theorists have predicted that hydrides such as calcium hydride or actinium hydride should superconduct at close to room temperature—and at a pressure considerably less than that needed for CSH.

From Science Magazine

Other theorists have predicted that hydrides such as calcium hydride or actinium hydride should superconduct at close to room temperature—and at a pressure considerably less than that needed for CSH.

From Science Magazine

Other theorists have predicted that hydrides such as calcium hydride or actinium hydride should superconduct at close to room temperature—and at a pressure considerably less than that needed for CSH.

From Science Magazine

Other theorists have predicted that hydrides such as calcium hydride or actinium hydride should superconduct at close to room temperature—and at a pressure considerably less than that needed for CSH.

From Science Magazine

But other heavy elements could, like actinium, which is a bit lighter with 89 protons and 89 electrons.

From New York Times