1. The decay of TI206 to Pb206 has a t1/2=4.2 min. Starting with 5x1022 atoms of TI206 calculate the number of atoms left after 42 min.
2. The decay of K40 to A 40 with a half-life of 1.2109 yrs.

1. Write an equation for the reaction.
2. A sample of moon rock is found to contaion 18% K40 to 82% Ar40 by mass. Calculate the age of the rock in years.

11. The decay of Tl206 to Pb206 has a t/2=4.2min. Starting with 51022 atoms of Tl206 calculate the number of atoms left after 42min. 12. The decay of K40 to Ar404 with a half-life of 1.2109yrs. A. Write an equation for the reaction. B. A sample of moon rock is found to contaion 18%K40 to 82%Ar40 by mass. Calculate the age of the rock in years