If a 100 g sample of a radioactive element decays to 25 g in 4 days what is the half-life of the element?

Answer 1

If a radioactive sample contains 1.25g of an isotope with a half-life of 4.0 days, then 0.625g (1/2) of the isotope will remain after 4.0 days, 0.3125g (1/4) after 8.0 days, 0.15625g (1/8) after 12.0 days, etc.

AT = A0 2(-T/H)

Answer 2

The half-life of this element will be 2 days since it will lose half its mass in the first two days, so 100g to 50g, then half the resulting mass in the next two days (now totaling 4 days), so 50g to 25g in four days.

So the half-life (in case the above was a bit rambling) is 2 days - at which point the element has lost half its original mass...which, of course, is what a half-life is :))

Answer 3

Half of any amount will be decayed 4 days after you start watching it.

It never goes all the way to zero.

For example, if you'll work it out, you'll find that after 100 days, there is

0.0000000298 of the original radioactive sample still remaining.

Answer 4

The half-life of the element is 2 days.

It has decayed to half, i.e 50 g in two days and then to half of that, i.e 25g in two half-lives.

Answer 5

it can't do that unless the decay products are all gasses.

Answer 6

The remaining 25 g is half of the original 100 g sample, so one half-life has passed. Therefore, the half-life of this radioactive element is 4 days.

Answer 7

9 years.