What percentage of a radioactive element will be left after 1 half-life?

Answer 1

Half life is pretty much self explanatory in that after they go through 1 half life half of the radioactive decay remains.

1/2 x 1/2 x 1/2 = 1/8 = 0.125 = 12.5%

or you can divide 100% by 2, 3 times and you'll get 12.5%

Answer 2

After every half-life, 1/2 of the previous amount is left over. So:

• After 1 half-life, 1/2 of the original amount is left.
• After 2 half-lives, 1/4 of the original amount is left (1/2 of 1/2).
• After 3 half-lives, 1/8 of the original amount is left.
• Etc.

Answer 3

After one half-life, 50%, or one-half of a radioactive element will be left.

Answer 4

Every half-life passed will lower the number of remaining atoms by 50%. So after 2 half-lives only 25% will remain.

After 7 half-lives only 0.78% remains.

Answer 5

After 3 half-lives, (1/2 x 1/2 x 1/2) = 1/8 remains. That's 12.5% .

Answer 6

After 6 half lives, the remaining will be (1/2)6 i.e 1/64 th of the initial amount.

Hence by percentage it would be 1.5625 %

Answer 7

That's (1/2) to the power 6. Actually, that's the answer as a fraction; to convert that to a percentage, you multiply it by 100.

Answer 8

.195

Answer 9

0.78%