Question

A certain radioactive element has a half-life of 6.93 s. If there are initially 1.00 x 10³ nuclei of that element, how many are left after 7.00 s? Give your answer to 2 significant figures.

Answer 1

Answer: 496.58

Solution:

we know, The following equation gives the quantitative relationship between the original number of nuclei present at time zero (N0) and the number (N) at a later time t.

N = N0e−λt.... (1)

Here, λ is the decay constant for the nuclide.

so, we get , since half life is given as 6.93. (t1/2)

Now, putting t = 7 sec in equation 1 ,

So, number of  nuclei of that element after 7 sec is 496.58. Ans.