Initially, there is 1 gram Nitrogen-13 (N-13) freshly prepared. The half-life of N-13 is 10 min. (i) Calculate the remaining weight of N-13 after 1 hr.

The half-life of beryllium-7 is about 53.3 days. (a) Determine the decay constant for beryllium-7. (b) What percentage of a sample remains undecayed after two weeks (1.21 ✕ 106 s)?

1) If the activity of a purely radioactive sample of 55Fe is measured to be 0.5 mCi. What is the number of nuclei of this isotope present after 5.4 years. 2) 226Ra (t₁/2 = 1600 y) alpha decays to the 1st excited state of nucleus X with branching ratio 6% and alpha decays to the ground state of X with branching ratio 94%. Calculate the partial half-life for the first mode transition (the one to the first excited state of X). 3) Fill the missing and decide the type of decay in the following decays: a) Co* → [ ] + Co b) ¹50 [ ] + [ ] + ¹5N 40 c) 10K + [ ] 18Ar d) 21 Po 84 e) ¹3 Be →>> 2a + [ ] ¹2Be + [ ]

3. (a) Calculate the decay constant for cobalt-60 (T1/2 = 5.26 Years) in units of week-¹ (b) Calculate the activity of a 5000-Ci cobalt-60 source after 10 years.