CHEM 120 Week 6 Lab; OL Lab 10; Nuclear Chemistry

Objectives: • Identify the differences between chemical reactions and nuclear reactions. • Identify the concept of radioactive decay. • Identify the nuclear changes associated with alpha, beta or gamma decay. • Write the products of nuclear reactions involving alpha, beta or gamma emissions. • Explain the concept of half-lives and complete half-life calculations. Not all atoms are stable. When atoms are born in a nuclear reactor, whether it be the heart of a star or a power plant, a portion of them are radioactive and are referred to as radioisotopes. Theseradioisotopes break down over time, releasing energy and transforming into more stable forms in processes known as radioactive decay. Depending upon the specific radioisotope, this process can be near instantaneous or take trillions of years. In this lab, you will explore radioactive decay as you learn about various types of radioactivity and half-life. Complete Table 1 below using the textbook, slides, and other course resources. Table 1: Type of radiation Give 1 example of each type. Ionizing X-rays Non-ionizing Radio waves electromagnetic Light (visible, infrared, and ultraviolet) particulate Beta Particles Exploration 1: How does alpha, beta, gamma, positron emission or electron capture affect a nucleus? Complete Table 2 below. Table 2: Radiation type Affect on atomic number of product Affect on number of protons in product Affect on mass number of product Alpha particle Decreased by 2 Loses 2 protons Decreased by 4 Beta particle Increased by 1 Gains 1 proton Unchanged Gamma particle Unchanged Unchanged Unchanged Positron Decreased by 1 Loses 1 proton Unchanged Electron capture Decreased by 1 Loses 1 proton Unchanged 1. In the space below, use X for the symbol of an element, Z for the atomic number and A for the mass number to write a general nuclide symbol. 2. An isotope of strontium has 38 protons and 52 neutrons. What is the nuclide symbol for an atom of this isotope? 3. Write the nuclear equation for the alpha decay of Thorium-232. 4. Write the nuclear equation for the beta decay of fluorine-19. 5. Write the nuclear equation for the gamma decay of fluorine-19. 6. Write the nuclear equation for the positron emission of sodium-23. 7. Suppose Potassium-41 undergoes electron capture. Write the nuclear equation that represents this process. Exploration 2: Modeling half-life Materials: Twizzlers, sheet of paper, or paper towel, and scissors In this activity, you will model half-life and complete the table with data. Measure the length of thematerial you will be cutting (time zero).The material you will be cutting represents a radioactive material with a half-life of 30 seconds. To simulate half-life, start by measuring the initial length of the paper and then set a timer for 1 minute.Cut the paper in half when the timer rings and measure the new length. Enter the data in the table below. Repeat the steps for three more half-lives. Time Remaining length 0 minute 28 cm 1st minute 14 cm 2nd minute 7 cm 3rd minute 3.5 cm 4th minute 1.25 cm Plot a graph of time on the X-axis and Radioactivity (length of paper) on theY-axis in the space below. Exploration 3: Half-life and medical imaging Technetium-99m is an important isotope used in medical imaging (the m stands for metastable). Each day healthcare professionals around the world use Technetium-99m in thousands of medical scans. This material has a very short half-life of about 6 hours and decays by gamma decay to Technetium-99. In this exercise, you will look at why half-life is an important concern and how it affects your health. 1. Technetium-99m has a half-life of 6 hours. Use this to answer the following questions: a. What percentage of Technituum-99m would remain in your body 24 hours after injection with this radioisotope? Assume that the initial percentage is 100%. b. In terms of radiation exposure, why is this short half-life beneficial? 2. Due to the short half-life of Technetium-99m, this material cannot be easily transported. However,Technetium-99m can be formed from the beta decay of Molybdenum-99, whichhas a half-life of about 2.75 days. Unfortunately, the world’s supply of molybdenum-99 is in jeopardy as the nuclear facilities that produce this material are beginning to cease operations. Use this information to answer the following questions: a. Write the nuclear equation for the beta decay of Molybdenum-99. b. If you have 50 grams of Molybdenum-99, how many grams will remain after 11 days? c. Would a good solution to the coming shortage of Molybdenum-99 be for hospitals to stockpile large amounts of Molybdenum-99? Why or why not?