http://www.ck12.org Chapter 24. Radioactivity and Nuclear Physics Version 2
b. It turns out both of these products are themselves radioactive; thePmproduct goes throughβ−decay
before it becomes stable and theCeproduct goes throughβ+decay before it reaches a stable isotope.
When all is said and done, what will Micol have left in her lab?Answers to Selected Problems
1..
2..
3..
4..
5..
6. a. SubstanceAdecays faster thanBb. SubstanceBbecause there is more material left to decay.
7. a.^21988 Ra→^21586 Rn+^42 He b.^15863 Eu→^15864 Gd+^0 − 1 e−c.^5322 Ti→^5323 Va+^0 − 1 e−d.^21183 Bi→^207
81 Tl+^42 He
8. a. 5× 1024 atoms b. Decay of a lot of atoms in a short period of time c. 2. 5 × 1024 atoms d.^12 e. 26.6 minutes
9. The one with the short half life, because half life is the rate of decay.
10. a. SubstanceB= 4 .6 g and substanceA= 0 .035 g b. substanceB
11. 1.2 g
12. 125 g
13. 0.46 minutes
14.t= 144 ,700 years
15. 0.0155 g
16. 17 years
17. 49,000 years