Worksheet # 3.7
Name _________________________________
Class __________________________________
All questions must be answered using the information provided in online Section 3 lecture 7,
Atoms and radioactivity.
1. Write the equation that describes the formation of Carbon-14 by the collision of a fast moving
neutron with the nucleus of a Nitrogen-14 atom:
2. Define half-life:
3. In two half-lives, what percentage of the original radioactive nuclei, remain unchanged?
___________________
4. When a neutron emits an electron and changes into a proton, the process is called beta decay.
Write the decay equation for Carbon-14 as it undergoes beta decay and forms Nitrogen-14:
5. Write the decay equation of a neutron changing into a proton as the neutron undergoes beta
decay:
6. Uranium-238 undergoes alpha decay. It has 92 protons and __________________ neutrons.
7. An alpha particle is the nucleus of a helium atom. Write the symbol for an alpha particle:
8. Write the decay equation for Uranium-238 as it undergoes alpha decay:
9. Thorium-234* undergoes gamma decay. Gamma is a photon of light. The photon does not have
mass or charge. When the Thoruium-234 undergoes gamma decay, its charge and mass do
not change. Write the decay equation for Thourium-234* as it undergoes gamma decay:
10. As we balance these equations, we rely two conservation principles. We believe in the
conservation of _______________ and ___________________.
11. A piece of paper will stop which type of radiation? ______________________
12. Aluminum foil will stop which two types of radiation? _________________ ____________________
13. A layer of lead is required to shield us from which type of radiation? ________________________
14. Thorium-234 undergoes beta decay. Please refer to the periodic table of elements, and write the
decay equation for Thoruim-234 as it undergoes beta decay:
15. An isotope of Chromium, Cr-55, undergoes beta decay. Refer to the periodic table of the
elements and write the decay equation for Chromium-55 as it undergoes beta decay:
Worksheet 3.7 continued
16. a. Chromium-55 has a half-life of 3.5 minutes. What fraction of the original Chromium-55
remains after fourteen minutes? _________________
b. If the original sample was 120 grams, how many grams of Cr-55 remain after 4 half-lives?
_________________________
17. a. The energy of a photon of light is directly proportional to its _________________.
b. The energy of a photon is inversely proportional to its ___________________. The smaller a
photon’s _____________, the more energy it has.
18. If a fresh sample of carbon=14 undergoes 40 beta decays per minute and an old sample of the
same mass has 10 beta decays per minute, how many half-lives have elapsed? _________________
19. A _____________________ field can be used to separate different types of radiation.