Radioactive decay is a fascinating process where unstable atomic nuclei shed particles or energy to become more stable. There are several types, including alpha, beta, and gamma decay, each with unique characteristics and effects on the nucleus.

Understanding nuclear stability is key to grasping why radioactive decay happens. The ratio of protons to neutrons in a nucleus determines its stability, with unstable nuclei undergoing decay to reach a more balanced state. This process is crucial in various fields, from medicine to energy production.

Types of Radioactive Decay

Types of radioactive decay

• Alpha decay involves emission of alpha particle (helium nucleus, $^4_2He$) from nucleus of heavy elements (uranium, radium) with too many protons, decreasing atomic number by 2 and mass number by 4
• Beta decay occurs in nuclei with imbalanced neutron-to-proton ratio
  • Beta minus ($\beta^-$) decay involves emission of electron from nucleus due to conversion of neutron into proton (carbon-14), increasing atomic number by 1 while mass number remains unchanged
  • Beta plus ($\beta^+$) decay involves emission of positron from nucleus due to conversion of proton into neutron (potassium-40), decreasing atomic number by 1 while mass number remains unchanged
• Gamma radiation involves emission of high-energy photons from nucleus when it transitions from excited state to lower energy state (cobalt-60), not changing atomic number or mass number

Balanced nuclear equations

• Alpha decay: $^A_ZX \rightarrow ^{A-4}_{Z-2}Y + ^4_2He$
• Beta minus decay: $^A_ZX \rightarrow ^A_{Z+1}Y + \beta^- + \bar{\nu}$ where $\bar{\nu}$ represents antineutrino
• Beta plus decay: $^A_ZX \rightarrow ^A_{Z-1}Y + \beta^+ + \nu$ where $\nu$ represents neutrino
• Gamma radiation: $^A_ZX^* \rightarrow ^A_ZX + \gamma$ where asterisk ($^*$) indicates excited nuclear state

Products of radioactive decay

• Determine atomic number and mass number of parent nuclide
• Apply changes to atomic number and mass number based on decay mode
  1. Alpha decay: $Z_{daughter} = Z_{parent} - 2$, $A_{daughter} = A_{parent} - 4$
  2. Beta minus decay: $Z_{daughter} = Z_{parent} + 1$, $A_{daughter} = A_{parent}$
  3. Beta plus decay: $Z_{daughter} = Z_{parent} - 1$, $A_{daughter} = A_{parent}$
• Identify daughter nuclide using periodic table (lead-206 from uranium-238 alpha decay)

Nuclear Stability and Radioactive Decay

Nuclear stability and decay

• Nuclear stability determined by ratio of protons to neutrons in nucleus
  • Stable nuclei have specific range of proton-to-neutron ratios (1:1 for light nuclei, 1:1.5 for heavy nuclei)
  • Unstable nuclei outside this range undergo radioactive decay (carbon-14, uranium-235)
• Nuclear stability curve (band of stability) shows relationship between number of protons and neutrons in stable nuclei
  • Nuclei above curve have too many neutrons and undergo beta minus decay (carbon-14)
  • Nuclei below curve have too many protons and undergo beta plus decay (potassium-40) or alpha decay for heavy nuclei (uranium-238)
• Factors affecting nuclear stability include nuclear forces (strong nuclear force binds nucleons, electrostatic repulsion between protons destabilizes nucleus) and neutron-to-proton ratio (more neutrons needed to maintain stability as number of protons increases)
• Radioactive decay occurs when unstable nucleus emits particles or energy to reach more stable configuration (uranium-238 to lead-206 through series of alpha and beta decays)