Nuclear decay is a spontaneous process where unstable atomic nuclei emit radiation, losing energy. This phenomenon underlies radiometric dating, nuclear medicine, and power generation, while also posing potential health risks due to ionizing radiation.
Conservation laws govern nuclear reactions, ensuring the preservation of mass-energy, charge, and nucleon number. Understanding these principles is crucial for predicting the outcomes of nuclear processes and their energy release.
Nuclear Decay
Process of nuclear decay
- Spontaneous process where unstable atomic nucleus loses energy by emitting radiation
- Occurs in radioactive materials containing unstable nuclei
- Radioactive materials emit ionizing radiation during decay (alpha particles, beta particles, gamma rays)
- Allows for radiometric dating to determine age of materials
- Used in nuclear medicine for diagnostic imaging and cancer treatment
- Enables generation of electricity through nuclear power plants
- Poses potential health risks due to exposure to ionizing radiation
- Rate of decay is characterized by half-life, the time it takes for half of a radioactive sample to decay
Conservation laws in nuclear reactions
- Conservation of mass-energy: Total mass-energy of closed system remains constant during nuclear reactions
- Mass can be converted into energy and vice versa ($E=mc^2$)
- Conservation of charge: Total electric charge of system remains constant during nuclear reactions
- Sum of charges of reactants equals sum of charges of products
- Conservation of nucleon number: Total number of protons and neutrons (nucleons) remains constant during nuclear reactions
- Sum of mass numbers (A) of reactants equals sum of mass numbers of products
Radioactive Decay
Parent vs daughter nuclei
- Parent nucleus: Original unstable atomic nucleus that undergoes radioactive decay
- Has specific number of protons and neutrons before decay process
- Daughter nucleus: Atomic nucleus that results from radioactive decay of parent nucleus
- Has different number of protons and/or neutrons compared to parent nucleus
- Can be stable or unstable, depending on type of decay and resulting nucleus
- Examples of parent-daughter relationships:
- Alpha decay: Uranium-238 (parent) decays into Thorium-234 (daughter) by emitting alpha particle
- Beta decay: Carbon-14 (parent) decays into Nitrogen-14 (daughter) by emitting beta particle
- Some radioactive isotopes undergo a series of decays known as a radioactive decay series
Energy release in decay reactions
- Alpha decay: Calculation of energy released
- $Q_α = (m_p - m_d - m_α)c^2$
- $Q_α$: Energy released
- $m_p$: Mass of parent nucleus
- $m_d$: Mass of daughter nucleus
- $m_α$: Mass of alpha particle
- $Q_α = (m_p - m_d - m_α)c^2$
- Beta decay: Calculation of energy released
- $Q_β = (m_p - m_d - m_e)c^2$
- $Q_β$: Energy released
- $m_p$: Mass of parent nucleus
- $m_d$: Mass of daughter nucleus
- $m_e$: Mass of electron (beta particle)
- $Q_β = (m_p - m_d - m_e)c^2$
- Gamma emission: Calculation of energy released
- $E_γ = hf$
- $E_γ$: Energy of gamma photon
- $h$: Planck's constant
- $f$: Frequency of gamma photon
- $E_γ = hf$
Nuclear Reactions and Energy
Nuclear binding energy
- Energy required to break apart a nucleus into its constituent protons and neutrons
- Explains the stability of nuclei and the energy released in nuclear reactions
Nuclear fission and fusion
- Nuclear fission: Process of splitting heavy atomic nuclei into lighter nuclei, releasing energy
- Nuclear fusion: Process of combining light atomic nuclei to form heavier nuclei, releasing energy