1. Rates of Nuclear Decay
These stone tools from the archaeological site in Cactus Hill, Virginia, are at least 15,000 years old.
Scientists estimated the age of the site based on rates of nuclear decay.

2. Half-life
Unlike chemical reaction rates, which vary with the conditions of a reaction, nuclear decay rates are constant.

3. Half-life
A half-life is the time required for one half of a sample of a radioisotope to decay.

4. Half-life
The half-life for the beta decay of iodine-131 is 8.07 days.

5. Half-life
The half-life for the beta decay of iodine-131 is 8.07 days.

6. Half-life
The half-life for the beta decay of iodine-131 is 8.07 days.

7. Half-life
The half-life for the beta decay of iodine-131 is 8.07 days.

8. Half-life
Every radioisotope decays at a specific rate. Half-lives can vary from fractions of a second to billions of years.

9. Decay Series of Uranium-238
Uranium-238 decays through a complex series of radioactive intermediates, including radon (Rn) gas. Interpreting Diagrams What is the stable end product of this series?
Stable Isotope

10. Half-life
Iridium-182 undergoes beta decay to form osmium-182. The half-life of iridium-182 is 15 minutes.
After 15 minutes, how much iridium-182 will remain of an original 1 gram sample?
0.5 g
b) After 30 minutes, how much iridium-182 will remain of the original 1 g sample?
0.25 g

11. Assessment Questions
Cesium-137 has a half-life of 30 years. You find a sample with 3 g of cesium-137. How much cesium-137 existed in the sample 90 years ago?
9 g
27 g
24 g
18 g

12. Assessment Questions
Cesium-137 has a half-life of 30 years. You find a sample with 3 g of cesium-137. How much cesium-137 existed in the sample 90 years ago?
9 g
27 g
24 g
18 g ANS: C

13. What factors influence nuclear decay rates?
Assessment Questions
What factors influence nuclear decay rates?
pressure
temperature
concentration
number of neutrons in nucleus

14. What factors influence nuclear decay rates?
Assessment Questions
What factors influence nuclear decay rates?
pressure
temperature
concentration
number of neutrons in nucleus ANS: D

15. Transmutation Reactions
The conversion of an atom of one element to an atom of another element is called transmutation.
Transmutation can occur by radioactive decay.
Transmutation can also occur when particles bombard the nucleus of an atom.

16. Transmutation Reactions
The first artificial transmutation reaction involved bombarding nitrogen gas with alpha particles.
The first artificial transmutation reaction involved bombarding nitrogen gas with alpha particles, as illustrated here. Interpreting Diagrams What particles were formed?

17. Transmutation Reactions
The elements in the periodic table with atomic numbers above 92, the atomic number of uranium, are called the transuranium elements.
All transuranium elements undergo transmutation.
None of the transuranium elements occur in nature, and all of them are radioactive.

18. Transmutation Reactions
Transuranium elements are synthesized in nuclear reactors and nuclear accelerators.
Fermilab is a major accelerator center located in Batavia, Illinois. The main accelerator is a ring that has a radius of 1.0 km.