After 240 years, 75% of the radioactive nuclides in a particular sample of an isotope have decayed. What is the half-life of this radioactive isotope?

Question

Quizplus · Accepted Answer

The half-life of a radioactive isotope is the time it takes for half of the radioactive nuclei in a sample to decay. After one half-life, 50% of the nuclei would remain. After two half-lives, 25% would remain, because 75% would have decayed. Since 75% decayed in 240 years, it means two half-lives have passed, making one half-life 240 years / 2 = 120 years.

After 240 Years, 75% of the Radioactive Nuclides in a Particular