Rf-267, with a half-life of 1.3 hours. If 5000 atoms of Rf-267 are synthesized, how many atoms were left after 3.9 hours?

Answer 1

Fraction remaining = 0.5ⁿ where n = number of half lives that have elapsed.

n = number of half lives = 3.9 hours / 1.3 hours = 3 half lives

Fraction remaining = 0.5³ = 0.125

Atoms remaining = 5000 x 0.125 = 625 atoms remain