Nuclear Reactions: Fission and Fusion

Fission

• Definition: A nuclear reaction where a neutron hits an atom's nucleus (e.g., uranium), making it unstable and causing it to split.
• Process:
  • The atom splits into two or three smaller atoms.
  • Releases additional neutrons that may trigger more reactions (chain reaction).
• Critical Mass: Minimum amount of material needed to sustain a chain reaction.
• Applications:
  • Controlled fission in nuclear power plants.
  • Part of nuclear bombs, combined with fusion.
• Mass Defect:
  • When atoms split, some mass seems missing.
  • "Missing" mass converts to energy (E=mc²).

Fusion

• Definition: Nuclear reaction where smaller nuclei combine to form a bigger nucleus.
• Energy Output: Produces more energy than fission.
• Natural Occurrence: Process that powers the sun.
• Applications:
  • Hydrogen bombs utilize a fission reaction to initiate fusion.
  • Creation of man-made elements.
• Cold Fusion: Concept contradicts thermodynamics as fusion typically requires high temperatures.

Radioactive Particles

• Beta Emission:
  • A neutron in the nucleus splits into a proton and a beta particle (negative charge).
• Alpha Decay:
  • Loss of two protons and two neutrons (helium nucleus).
• Gamma Emission:
  • Release of energy, not a particle.
• Neutron Emission:
  • Loss of a neutron, decreasing atomic mass.

Band of Stability

• Definition: Range of neutron and proton numbers where an atom is stable.
• Instability:
  • Too many or too few neutrons outside the band lead to decay (neutron, beta, alpha decay).

Stability Calculation

• Formula: Number of protons x 1.5 = Range for stable neutrons.
• Example with Carbon-14:
  • Protons = 6, Mass number = 14
  • Neutrons = Mass number - Protons = 8
  • Stability check: 6 x 1.5 = 9 (8 falls within range, therefore stable)

Conclusion

• Use digital notebook for further examples and practice problems.