The thallium subscript 81 superscript 208 baseline tl nucleus is radioactive, with a half-life of 3.053 min. at a given instant, the activity of a certain sample of thallium is 2400 bq. using the concept of a half-life, and without doing any written calculations, determine what the activity 9 minutes later is.
(a) 150 bq
(b) 2400 bq
(c) 1200 bq
(d) 600 bq
(e) 300 bq

(E) 300 bq

Explanation:

Half life is the amount of time taken by a radioactive material to decay to half of its original value.

Radioactive decay process is a type of process in which a less stable nuclei decomposes to a stable nuclei by releasing some radiations or particles like alpha, beta particles or gamma-radiations. The radioactive decay follows first order kinetics.

Half life is represented by

Half life of Thallium-208 = 3.053 min

Thus after 9 minutes , three half lives will be passed, after ist half life, the activity would be reduced to half of original i.e. , after second  half life, the activity would be reduced to half of 1200 i.e. ,  and after third half life, the activity would be reduced to half of 600 i.e. ,

Thus the activity 9 minutes later is 300 bq.

answers: to make sure that all of the broken pieces of tablet were added to the water, to allow for fair comparison of all three trials, with different particle sizes to avoid experimental error

since electrons are negative the answer is neagtaive