See Also: Actinium(medicine)
actinium(dictionary)

actinium (iou)



actinium noun. E20.
[formed as ACTINISM + -IUM.]
A radioactive metallic chemical element, atomic no. 89, which is the first element of the actinide series and is found in small quantities in pitchblende. (Symbol Ac.)
'actinoid noun = ACTINIDE M20.
'actinon noun (a) History of Science an isotope of radon, radon-219; (b) = ACTINIDE: E20.