Question

The half life of a radioactive isotope X is 3 s. Initially there are 8000 atoms of this isotope in the sample. Calculate (i) its decay constant (ii) time t in which 1000 atoms are active in the sample.
Solution:
T1/2 = 3 S, N0 = 8000
(i) We know that

Answer 1

Explanation:

i.k=0.693/t1/2

k=0.693/3

=0.231

ii)8000--->4000------>2000----->1000

three half life's

3*3=9 minutes