Notes on Radioactive Decay and Alpha Particles

Understanding Radium-226 Decay

  • Radium-226 Characteristics

    • Atomic Number: 88 (indicating 88 protons)
    • To find the number of neutrons:
    • Formula: Neutrons = Mass Number - Atomic Number
    • Neutrons=(226−88)=138Neutrons = (226 - 88) = 138

  • Alpha Decay of Radium

    • Radium-226 undergoes radioactive decay by emitting an alpha particle (Helium nucleus).
    • Properties of Alpha Particle:
    • Mass: 4 units
    • Protons: 2

  • Balancing the Reaction

    • Conservation of Protons:
    • Protons before decay (radium): 88
    • Protons after decay = Protons before - Protons lost in alpha particle
    • 88−2=8688 - 2 = 86
    • The remaining atomic number (86) corresponds to Radon (Rn).

  • Balancing Mass Number

    • Mass number before decay: 226
    • Mass after decay = Mass before - Mass of alpha particle
    • 226−4=222226 - 4 = 222

  • Conclusion of Radium Decay

    • Radium-226 emits an alpha particle and transforms into Radon-222:
    • Reaction: Ra226<em>88→Rn222</em>86+He24\text{Ra}^{226}<em>{88} \rightarrow \text{Rn}^{222}</em>{86} + \text{He}^{4}_{2}

Alpha Radiation

  • Safety of Alpha Particles
    • Alpha particles are the safest form of radiation; they can be blocked by:
    • Paper
    • Clothing
    • They are large particles, making them relatively easy to shield against.

Example: Americium-241 Decay

  • Americium Characteristics

    • Mass Number: 241
    • Atomic Number: 95

  • Alpha Emission

    • Similar to radium decay, Americium also emits an alpha particle.

  • Balancing the Reaction for Americium

    • Protons:
    • 95−2=9395 - 2 = 93
    • Corresponds to Neptunium (Np).
    • Mass:
    • 241−4=237241 - 4 = 237

  • Conclusion of Americium Decay

    • Americium-241 emits an alpha particle and transforms into Neptunium-237:
    • Reaction: Am241<em>95→Np237</em>93+He24\text{Am}^{241}<em>{95} \rightarrow \text{Np}^{237}</em>{93} + \text{He}^{4}_{2}
Summary
  • In radioactive decay involving alpha particles, both the atomic number and mass number must be balanced before and after the decay.
  • Understanding how to find the resulting elements after decay is crucial and involves using the periodic table to identify them based on their atomic numbers.