17_Lecture - Read-Only

Chapter Overview

• Title: Radioactivity and Nuclear Chemistry

• Author: Nivaldo J. Tro

• Institution: Southwestern Oklahoma State University

Introduction to Radioactivity and Its Applications

• Nuclear Medicine: Uses radioactivity to visualize internal organs.

Case Study: Diagnosing Appendicitis

• Procedure: Radioactively tagged antibodies accumulate in infected appendices, emitting detectable radiation on photographic film.

Fundamental Concepts of Radioactivity

• Definition: Radioactivity refers to the emission of energetic particles from the nuclei of unstable atoms.

Historical Background of Radioactivity

Discovery by Antoine-Henri Becquerel

• Year: 1896

• Hypothesis: Emission of X-rays linked to the phosphorescence of potassium uranyl sulfate.

• Experiment: Exposure of photographic plates to sunlight with phosphorescent crystals led to clear exposure, supporting his hypothesis.

• Conclusion: Uranium within crystals emitted these rays; termed "uranic rays."

• Retraction: Discovered radiation emitted even without light; affirming constant emissions.

Contributions of Marie Sklodowska Curie

• Edits: Conducted doctoral research on uranic rays.

• Discovery of Elements: Identified polonium (named after Poland) and radium.

• Recognition: Won Nobel Prizes in Physics (1903) and Chemistry (1911).

Types of Radioactivity

Particle Emission Overview

• Types: Alpha (α), Beta (β), Gamma (γ) rays, and positrons.

• Stability: Unstable nuclei emit particles for stability; characterizations of radioactivity pioneered by Rutherford.

• Nuclide: Specific isotope; parent nuclide is original atom, and daughter nuclides are products of decay.

Characteristics of Radiation Types

Alpha Radiation

• Composition: 2 protons and 2 neutrons

• Ionizing Power: High

• Penetrating Power: Low (can be stopped by paper or clothing)

Beta Radiation

• Process: Emission of an electron; neutron transforms into a proton.

• Ionizing Power: Intermediate

• Penetrating Power: Greater than alpha; metal or thick wood required to stop.

Gamma Radiation

• Nature: Electromagnetic radiation, no mass or charge.

• Ionizing Power: Low

• Penetrating Power: High; requires dense materials like lead or concrete to shield.

Concept of Half-Life

• Definition: Time required for half of a radioactive sample to decay.

• Implication: Assesses age of remnants; e.g., carbon-14 with a half-life of 5730 years.

Natural Radioactive Decay Series

• Example: Uranium-238 decays to lead-206 gradually through intermediate isotopes.

Detecting Radioactivity

• Methods: Film badges, Geiger-Müller counters, scintillation counters.

• Function: Measure exposure and monitor environmental radiation levels.

Health Impacts of Radiation

Acute Radiation Damage

• Affected Groups: Rapidly dividing cells like those in the immune system are most susceptible.

• Outcome: Can lead to radiation sickness or death.

Cancer Risk

• Long-term Exposure: Increases likelihood of mutations leading to cancer; DNA damage is a significant factor.

Genetic Defects

• Potential Risks: Damage to reproductive cell DNA may result in genetic abnormalities in offspring.

Nuclear Applications in Medicine

Radiotherapy

• Technique: Focused exposure to malignant tumors using gamma rays.

Imaging Techniques

• Isotope Scans: Use of specific isotopes to visualize internal structures, such as Technetium-99 for bone scans.

Overview of Nuclear Power

Energy Generation

• Mechanism: Fission reactions in reactors generate heat for electricity.

Accidents and Safety Measures

• Chernobyl & Fukushima: Notable nuclear disasters highlighting safety failures.

Waste Disposal Issues

• Current Challenges: Long-term storage solutions are needed due to the hazardous nature of nuclear waste.

Future Considerations in Nuclear Energy

Nuclear Fusion

• Mechanism: Fusion of lighter nuclei to heavier forms, requiring extreme temperatures.

Research Directions

• Challenges: Feasibility for electric power generation continues to be a major scientific endeavor.

Summary of Key Learning Objectives

• Ability to write nuclear equations for various decay types.

• Understanding of half-life and radiocarbon dating.