After 4.00 years, 3.972 g of a radioisotope remains from a sample that had an original mass of 4.00g. Calculate the half-life of this mystery radioisotope. How much of the radioisotope remains after 20.0 years?

After each half-life, half of the existing radioactive atoms have decayed into atoms of a new element. What are two ways that transmutation can occur?

1 Expert Answer. Because the half-life is 6 hours, the starting amount will be halved every 6 hours. Because there are 18 total hours, the starting amount will be divided by 2 (halved) three times. You will then have 1/6 of the starting amount, thus being 384 grams/ 6 = 48 grams