Suppose 128 radioactive atoms have a half-life of 15 seconds. Approximately how many radioactive atoms will be left after 60 seconds

8 electrons

Explanation:

Number of atoms = 128

Half life = 15 s

After each half life, the number of atoms reduces by half. So we need to determine how many half lives are in 60s.

Number of half lives = 60s / 15s = 4

After the first life;

Number of electrons left = 128 / 2 = 64

After the second life;

Number of electrons left = 64 / 2 = 32

After the third half life;

Number of electrons left = 32 / 2 = 16

After the fourth half life;

Number of electrons left = 16 / 2 = 8