noun. A radioactive element found in uranium ores, used in equilibrium with its decay products as a source of alpha rays. Its longest lived isotope is Ac-227 with a half-life of 21.77 years. Atomic number 89; melting point 1,050°C; boiling point 3,198°C; specific gravity (calculated) 10.07; valence 3. cross-reference: Periodic Table.

noun. A supposed chemical element found associated with zinc. Its chemical and physical properties have not been fully investigated.

noun. undefined

noun. A radioactive substance found by Debierne to exist in the residues remaining from pitchblende after the extraction of the uranium: a new radio-element closely related in its chemical behavior to lanthanum, from which it has not as yet been found possible to separate it completely.

noun. A supposed metal, said by Phipson to be contained in commercial zinc; -- so called because certain of its compounds are darkened by exposure to light.

noun. a radioactive, metallic chemical element (symbol: Ac) with an atomic number of 89; found in uranium ores

noun. a radioactive element of the actinide series; found in uranium ores

"In collaboration with Rona, she applied her method to the study of the ranges of alpha particles emitted from actinium and polonium. 6 7"

actinium rays  

chemical element  element  

cerium  cometary  cottony  dagont  disc-shaped