U-238 Radioactive Decay Chemistry Lab

Name ________________________ Partner _________________ Date _________________ Per ____

Purpose To determine the natural decay of uranium-238 and to create the uranium-238 decay series. Background The radioactive decay of uranium has been extensively studied due to its abundance in nature and the important role uranium plays in nuclear power and weapons. The uranium-238 isotope is the most abundant isotope found in nature. Uranium-238 undergoes a slow radioactive decay to lead-206 through a series of steps called the Uranium decay series. The nuclear forces that hold the nucleus of an atom together, at nuclear distances, are usually stronger than the electric forces that would make it fly apart. Radioactive isotopes are unstable and undergo spontaneous nuclear reactions, emitting particles and/or wavelike radiation. The decay of any one nucleus cannot be predicted, but a large group of identical nuclei decay at a predictable rate. This predictability can be used to estimate the age of materials that contain radioactive isotopes. Fission is the splitting of a large nucleus into smaller pieces. Fusion is the joining of two nuclei at extremely high temperature and pressure, and is the process responsible for the energy of the sun and other stars. Natural uranium also contains 0.7% of uranium-235. When bombarded with neutrons, uranium235 will undergo nuclear fission and break into two lighter elements, releasing substantial amounts of energy in the process. This is the principle behind both nuclear weapons and nuclear power. This graphic represents one possible decay chain of U-238. Use this information to complete this lab. At least 9 of these decays are followed closely by  radiation.

Procedure 1. Use beans to represent the nucleus of a U-238 atom. Use the white beans to represent neutrons and the red beans to represent protons. How many protons ________ and neutrons ________ do you need? 2. What kind of decay is it ? ________ Move beans to represent the decay. For alpha remove 2 protons and 2 neutrons. Place the nucleons that you removed into a small beaker. For beta decay replace one of the neutrons in the nucleus with a proton. Write a nuclear equation to represent the decay of U-238.

3. Continue manipulating the beans to represent the next steps in the decay chain. Write correct nuclear reaction equations for the next 4 decay cycles. Each time you should manipulate the appropriate beans and be sure to put any beans removed (not the changed neutron  proton beans) into the small beaker. Write the equations below:

4. Continue the decay chain, each time you should manipulate the appropriate beans and be sure to put any beans removed (not the changed neutron  proton beans) into the small beaker. You do not need to include any more equations. When you finally reach the stable isotope, you are done. Count up all the beans. How many protons ________ and neutrons ________ did you remove?

5. Complete the graph of mass number (y-axis) vs. atomic number (x-axis) for each element in the series. Write the element’s symbol at its point on the graph and connect the appropriate points in order of decay with an arrow. Be sure to label the graph.

1. What are the three types of radiation?

2. Which type of radiation is the most penetrating? ___________________________________ 3. Why do some isotopes undergo radioactive decay?

4. Define half life.

5. a) Write the half life of U-238 in scientific notation? ________________________________ _ b) How many years is this (in words)?

6. a) Which isotope is the least stable? ________________________ _____ b) Which isotope is the most stable? __________________________ ___ (hint: look at the half-lives) 7. List the elements that have more than one isotope in this U-238 decay chain. Include the different isotopes for these elements.