CHEM 120 Week 6 Lab: Nuclear Chemistry

Week 6 Lab: Nuclear Chemistry

Objectives

The objective of this lab is to provide a detailed exploration of nuclear chemistry and its underlying concepts. By the conclusion of the lab, students should be able to:

• Distinguish between chemical and nuclear reactions.

• Explain radioactive decay and identify nuclear changes associated with alpha, beta, and gamma emissions.

• Accurately write nuclear reactions involving alpha, beta, or gamma decay.

• Define the concept of half-life and perform related calculations.

• Identify subatomic particles and the energies involved in nuclear reactions.

• Recognize various modes of radioactive decay, including alpha, beta, gamma, and electron capture, through the concepts of nuclear mass defect and binding energy.

• Describe the real-world applications of radioactive isotopes in nuclear medicine, radiocarbon dating, and nuclear power.

• Understand the scientific principles of carbon dating.

Radioactivity is not confined to nuclear power plants; it naturally exists in the environment around us. In this virtual lab, students examined the nucleus of the atom and investigated why some isotopes are stable while others are unstable. By simulating alpha, beta, and gamma decay, learners observed radioactive processes in a safe and controlled digital setting.

Part 1: Labster Lab – Nuclear Chemistry

Purpose

The aim of this virtual experiment was to:

• Examine subatomic particles and their associated energies in nuclear reactions.

• Understand and apply the concept of half-life.

• Explore the various types of radioactive decay.

• Investigate the mechanism of carbon dating.

• Analyze practical applications of radioactive isotopes, particularly in medicine and industry.

Observations

During the lab simulation, the following key observations were made:

1. Like charges repel each other due to electrostatic forces.

2. Nuclear forces act over extremely short ranges, confined within the nucleus.

3. The concept of half-life is useful in estimating when a specific atom is likely to decay.

Radiation Types and Their Effects

Radiation Type	Effect on Atomic Number	Effect on Protons	Effect on Mass Number
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

General Nuclide Symbol

The general format for representing nuclides is:

ZAX^{A}_{Z}X

Where A is the mass number, Z is the atomic number, and X is the chemical symbol.

Example: Strontium Isotope

• Protons = 38

• Neutrons = 52

• Mass Number = 38 + 52 = 90

• Atomic Number = 38

• Element = Strontium (Sr)

Nuclide Symbol: ⁹⁰Sr₃₈

Nuclear Equations

• Gamma decay of fluorine-19:
  ¹⁹F → ¹⁹F + γ

• Positron emission of sodium-23:
  ²³Na → ²³Ne + e⁺

• Electron capture of potassium-41:
  ⁴¹K + e⁻ → ⁴¹Ar

Part 2: Half-Life and Medical Imaging

Technetium-99m (Tc-99m) is a widely used radioisotope in diagnostic imaging. With a half-life of 6 hours, it undergoes gamma decay to form stable Technetium-99, making it ideal for short-term medical procedures.

Question 9

a. What percentage of Technetium-99m would remain in your body 24 hours after injection?
After 24 hours, which equals four half-lives (24 ÷ 6), 6.25% of the original isotope would remain.

b. Why is the short half-life beneficial?
The short half-life minimizes long-term exposure to radiation, reducing the likelihood of harmful effects such as dizziness, chest discomfort, or irregular heartbeat. Additionally, it ensures effective imaging while quickly leaving the body.

Question 10

a. Write the nuclear equation for the beta decay of Molybdenum-99.
⁹⁹Mo → ⁹⁹mTc + β⁻

b. If you have 50 grams of Molybdenum-99, how many grams will remain after 11 days?
Using half-life calculations, about 3.12 grams of Mo-99 would remain after 11 days.

c. Would stockpiling Molybdenum-99 solve the shortage issue? Why or why not?
No, stockpiling would not resolve the issue due to the isotope’s short half-life and instability. Continuous production is necessary to ensure sufficient supply for medical imaging.

Reflection

Another important medical isotope is Iodine-131, which is utilized in both the diagnosis and treatment of thyroid cancer. It is administered orally in either liquid or capsule form. With a half-life of 8.06 days, I-131 undergoes both beta and gamma decay.

While highly effective, Iodine-131 poses potential health risks if exposure is excessive. External exposure may result in skin and eye burns, while internal exposure can severely damage the thyroid gland. Since the thyroid cannot differentiate between stable and radioactive iodine, the absorption of I-131 increases the risk of thyroid-related complications, including cancer.

References

Centers for Disease Control and Prevention. (2018, April 4). CDC radiation emergencies: Iodine-131. U.S. Department of Health and Human Services. Retrieved October 3, 2022, from https://www.cdc.gov/nceh/radiation/emergencies/isotopes/iodine.htm

CHEM 120 Week 6 Lab: Nuclear Chemistry