Chapter 9: Radioactivity and Nuclear Processes PDF

9.1 Discovery of Radioactivity Key Figures: ○ Wilhelm Röntgen: Discovered X-rays. ○ Henri Becquerel: Identified radioactivity in 1896. ○ Marie and Pierre Curie: Named the phenomenon "radioactivity" and shared the 1903 Nobel Prize with Becquerel. 9.2...

9.1 Discovery of Radioactivity Key Figures: ○ Wilhelm Röntgen: Discovered X-rays. ○ Henri Becquerel: Identified radioactivity in 1896. ○ Marie and Pierre Curie: Named the phenomenon "radioactivity" and shared the 1903 Nobel Prize with Becquerel. 9.2 What is Radioactivity? Types of Radiation: ○ Alpha (α): Helium nuclei (2 protons, 2 neutrons), charge +2. ○ Beta (β): Electrons, charge -1; Positrons (β⁺), charge +1. ○ Gamma (γ): High-energy electromagnetic radiation, no mass or charge. Wavelength and Frequency: ○ Wavelength (λ\lambdaλ) and frequency (ν\nuν) are inversely related (λ=cν\lambda = \frac{c}{\nu}λ=νc​). ○ Gamma rays are highly energetic and invisible to the human eye. 9.3 Nuclear Radiation Stable vs. Unstable Isotopes: 1. 264 naturally occurring isotopes are stable. 2. Radioactivity occurs in isotopes with an imbalance in proton-to-neutron ratio. Types of Decay: 1. Beta Emission: Neutron → Proton + Electron (ejected). 2. Alpha Emission: Helium nucleus ejection, reducing atomic number by 2 and mass number by 4. 3. Positron Emission: Proton → Neutron + Positron (ejected). 4. Gamma Emission: High-energy state → Ground state, no change in atomic/mass numbers. 5. Electron Capture: Nucleus captures an electron, reducing atomic number by 1. 9.4 Half-Life Definition: Time for half a radioactive sample to decay. Examples: ○ Iodine-131 decays via beta and gamma emissions. 9.5 Measuring Radioactivity Detection Tools: ○ Dosimeters: Measure radiation exposure. ○ Geiger Counters: Detect radiation by ionization. ○ Scintillation Counters: Measure radiation quantitatively.  Penetration Power: ○ Alpha: Least penetrating, stopped by paper. ○ Beta: Penetrates paper, stopped by thin lead. ○ Gamma: Highly penetrating, stopped by thick lead. 9.6 Radiation Dosimetry.pdated Section: Radiation Dosimetry Effects of Radiation Exposure 25 rem: Whole-body exposure noticeable in blood count. 100 rem: Causes symptoms of radiation sickness. 400 rem: Causes death within one month in 50% of exposed individuals. 600 rem: Almost invariably lethal within one month. 50,000 rem: Required to kill bacteria. 1,000,000 rem (10⁶ rem): Required to inactivate viruses. Effects: ○ 100 rem: Radiation sickness. ○ 600 rem: Lethal dose within a month. 9.7 Nuclear Medicine Use of radionuclides for diagnosis and treatment. 9.8 Nuclear Fusion Process: Fusing light nuclei (e.g., hydrogen) into heavier ones (e.g., helium). Applications: ○ Energy source in stars. ○ Creation of transuranium elements. 9.9 Nuclear Fission Process: Splitting heavy nuclei (e.g., Uranium-235) into smaller ones, releasing energy. Applications: ○ Controlled: Nuclear reactors. ○ Uncontrolled: Nuclear weapons. Waste Management: ○ Spent fuel disposal at sites like Yucca Mountain.