| 释义 | 
		Definition of actinium in English: actiniumnoun akˈtɪnɪəmækˈtɪniəm mass nounThe chemical element of atomic number 89, a radioactive metallic element of the actinide series. It is rare in nature, occurring as an impurity in uranium ores.  Example sentencesExamples -  The first four actinide elements, actinium, thorium, protactinium and uranium are naturally occurring and have been known for a considerable time.
 -  Along the way, these disintegration series produce radioactive isotopes of protactinium, thorium, actinium, radium, francium, radon, astatine, polonium, bismuth, lead, thallium and mercury.
 -  Francium was discovered in 1939 by the French physicist Marguerite Perey while she was analyzing the products formed during the radioactive decay of actinium.
 -  A proposal was patented for a ceramic block pessary using radioactive elements such as thorium, actinium and even radium.
 -  Actinides - the radioactive chemical elements that span from actinium to lawrencium on the periodic table - have generated a great deal of interest in recent years.
 
 
 Origin   Early 20th century: from Greek aktis, aktin- 'ray' + -ium. Rhymes   aluminium, condominium, delphinium    Definition of actinium in US English: actiniumnounakˈtinēəmækˈtɪniəm The chemical element of atomic number 89, a radioactive metallic element of the actinide series. It is rare in nature, occurring as an impurity in uranium ores.  Example sentencesExamples -  Actinides - the radioactive chemical elements that span from actinium to lawrencium on the periodic table - have generated a great deal of interest in recent years.
 -  A proposal was patented for a ceramic block pessary using radioactive elements such as thorium, actinium and even radium.
 -  Francium was discovered in 1939 by the French physicist Marguerite Perey while she was analyzing the products formed during the radioactive decay of actinium.
 -  Along the way, these disintegration series produce radioactive isotopes of protactinium, thorium, actinium, radium, francium, radon, astatine, polonium, bismuth, lead, thallium and mercury.
 -  The first four actinide elements, actinium, thorium, protactinium and uranium are naturally occurring and have been known for a considerable time.
 
 
 Origin   Early 20th century: from Greek aktis, aktin- ‘ray’ + -ium.     |