'For the radioactive isotope Actinium-227, it's 21.8 years'
Half-life
SCIENCE: For the radioactive isotope Actinium-227, its 21.8 years
For the radioactive isotope Actinium-227, it's 21.8 years
For the radioactive isotope Actinium-227, it's 21.8 years
SCIENCE
Half-life
SCIENCE