CHEM 120 Week 6 Lab: Nuclear Chemistry
Student Name
Chamberlain University
CHEM-120 Intro to General, Organic & Biological Chemistry
Prof. Name
Date
Week 6 Lab: Nuclear Chemistry
Objectives
The purpose of this lab is to enhance understanding of nuclear chemistry by addressing the following key learning objectives:
- Differentiate between chemical reactions and nuclear reactions.
- Explain the concept of radioactive decay.
- Identify the nuclear transformations that occur during alpha, beta, and gamma decay.
- Write balanced nuclear equations for alpha, beta, and gamma emissions.
- Define half-life and perform half-life calculations.
- Recognize the subatomic particles and energy changes involved in nuclear reactions.
- Compare common types of radioactive decay—alpha, beta, gamma, and electron capture—based on differences in mass defect and binding energies.
- Discuss practical applications of radioactive isotopes, such as nuclear medicine, radiometric dating, and nuclear power.
- Describe the principles and process of carbon dating.
Introduction to Radioactivity
A common misconception is that radioactivity exists only in nuclear power plants. In reality, it is a natural phenomenon occurring all around us. Some atoms are inherently unstable, and their nuclei spontaneously emit radiation as they transform into more stable forms. This process, called radioactive decay, produces alpha particles, beta particles, or gamma rays, each with distinct characteristics.
Through the simulation, students observe nuclear behavior at the subatomic level using a holofloor visualization tool. This allows them to examine how protons and neutrons interact, how nuclear stability varies between isotopes, and how each decay type impacts atomic properties.
Radioisotopes are produced naturally in stars, artificially in reactors, and during particle interactions. They lose energy over time by emitting radiation until they reach a stable configuration. Understanding these processes is crucial for fields like medicine, archaeology, and energy production.
Part 1: Complete Labster Lab – Nuclear Chemistry
Purpose
1. Purpose:
The aim of this experiment was to identify subatomic particles and the energy changes involved in nuclear reactions, understand the concept of half-life, examine various modes of radioactive decay, and explore applications of radioactive isotopes such as medical imaging and carbon dating.
Observations
2. Observations:
Three notable observations from the simulation include:
- Like charges repel—two positively charged particles will push away from each other.
- The nuclear strong force acts only over extremely short distances, functioning exclusively within the atomic nucleus.
- The concept of half-life enables scientists to estimate the time required for a specific quantity of a radioactive atom to decay.
Nuclear Decay Effects
3. Complete the table below:
| Radiation Type | Effect on Atomic Number of Product | Effect on Number of Protons in Product | Effect on Mass Number of Product |
|---|---|---|---|
| Alpha particle | Decreases by 2 | Decreases by 2 | Decreases by 4 |
| Beta particle | Increases by 1 | Increases by 1 | No change |
| Gamma particle | No change | No change | No change |
| Positron | Decreases by 1 | Decreases by 1 | No change |
| Electron capture | Decreases by 1 | Decreases by 1 | No change |
Nuclide Symbols and Nuclear Equations
4. 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.
ZAX^{A}_{Z}X
5. An isotope of strontium has 38 protons and 52 neutrons. What is the nuclide symbol for an atom of this isotope?
- Protons: 38
- Neutrons: 52
- Mass number: 38+52=9038 + 52 = 90
- Atomic number: 38 (Strontium, symbol Sr)
Nuclide symbol:
3890Sr^{90}_{38}Sr
6. Write the nuclear equation for the gamma decay of fluorine-19.
919F→919F+γ^{19}_{9}F \rightarrow ^{19}_{9}F + \gamma
7. Write the nuclear equation for the positron emission of sodium-23.
1123Na→β++1023Ne^{23}_{11}Na \rightarrow \beta^{+} + ^{23}_{10}Ne
8. Suppose Potassium-41 undergoes electron capture. Write the nuclear equation that represents this process.
1941K+e−→1841Ar^{41}_{19}K + e^{-} \rightarrow ^{41}_{18}Ar
Part 2: Half-Life and Medical Imaging
Technetium-99m (Tc-99m), used extensively in nuclear medicine, has a short half-life of 6 hours and decays via gamma emission to form Tc-99. This short half-life minimizes patient radiation exposure while still enabling effective imaging.
9a. What percentage of Technetium-99m would remain in your body 24 hours after injection with this radioisotope?
CHEM 120 Week 6 Lab: Nuclear Chemistry
Formula:
A=P×(12)t/hA = P \times \left(\frac{1}{2}\right)^{t/h}
Where:
- PP = initial amount (100%)
- tt = elapsed time = 24 hours
- hh = half-life = 6 hours
A=100×(12)24/6=100×116=6.25%A = 100 \times \left(\frac{1}{2}\right)^{24/6} = 100 \times \frac{1}{16} = 6.25\%
Answer: 6.25% remains after 24 hours.
9b. In terms of radiation exposure, why is this short half-life beneficial?
A shorter half-life means the isotope decays quickly, reducing the duration of radiation exposure and minimizing the risk of adverse effects such as tissue damage or organ stress.
10a. Write the nuclear equation for the beta decay of Molybdenum-99.
4299Mo→4399Tc+β−^{99}_{42}Mo \rightarrow ^{99}_{43}Tc + \beta^{-}
10b. If you have 50 grams of Molybdenum-99, how many grams will remain after 11 days?
Half-life (hh) = 2.75 days
Number of half-lives: 11/2.75=411 / 2.75 = 4
Remaining amount: 50×(12)4=50×116=3.125 g50 \times \left(\frac{1}{2}\right)^{4} = 50 \times \frac{1}{16} = 3.125 \, \text{g}
10c. 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?
No. Because Mo-99 has a relatively short half-life, stockpiling would lead to significant decay before use, making it ineffective. Continuous production is necessary to ensure adequate supply for medical diagnostics.
Reflection
For this reflection, Iodine-131 is considered. This isotope is widely used for both the diagnosis and treatment of thyroid disorders, including thyroid cancer. It is commonly administered orally as a capsule or liquid and is easily soluble in water or alcohol.
- Half-life: Approximately 8.06 days.
- Decay type: Beta decay and gamma emission.
- Applications: Used in targeted therapy for thyroid disease and in diagnostic imaging.
- Safety concerns:
- External exposure can cause burns to skin or eyes.
- Internal exposure, especially via inhalation or ingestion, can result in thyroid damage or increase the risk of thyroid cancer.
- Because the thyroid absorbs both radioactive and stable iodine indiscriminately, accidental environmental release of I-131 can lead to widespread contamination through food, water, or air.
CHEM 120 Week 6 Lab: Nuclear Chemistry
References
Centers for Disease Control and Prevention. (2018, April 4). CDC radiation emergencies: Iodine-131. Retrieved from https://www.cdc.gov/nceh/radiation/emergencies/isotopes/iodine.htm