The heaviest known isotope of hydrogen is called tritium, . it decays by beta emission, and has a half-life of 12.3 years. what fraction of a tritium sample will remain after 5.20 years?

= 3/4

Explanation:

Half life is the time taken by a radioactove element to decay by half of its original mass.

The half life of tritium is 12.3 years , therefore it would take 12.3 years for tritium to decay to a half its original mass.

Using the formula;

New mass = Initial mass × (1/2)^n ; where n is the number of half lives.

n = 5.2 years/12.3 years

  = 52/123

Therefore;

New mass = 1 × (1/2)^(52/123)

                  = 0.74599

                  = 0.75

The fraction of a tritium sample after 5.20 years will be approximately 3/4