the radioactive series that starts with uranium 235 and ends with a stable isotope of lead of mass number 207.
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Origin of actinium series
First recorded in 1955–60
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for actinium series
a radioactive decay series that starts with uranium-235 and ends with lead-207
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012