The half life of thallium 201 is 21.5 hours. We have 98 g of thallium 201 how many grams will be left after 10 half-lives?

                     0.0957 g

Explanation:

                    Half life is the time required by the substance to decay to half of its initial mass. Most often exponential decays of radioactive substances are explained by half life. Half life remains constant throughout the life of decay.

It is given as;

                                      N(t)  =  N₀ (1/2)^t/t1/2

Where;

           N(t)  =  Amount remaining after certain time

           N₀  =  The starting initial amount

           t1/2  =  Half life of given substance

Putting values,

                                      N(t)  = 98 × (1/2)^215/21.5

                                      N(t)  = 0.0957 g