Fission, Fusion and Nuclear Decay
Describe the physical properties that constrain the behavior of interacting nuclei, subatomic particles, and nucleons.
- The strong force is exerted at nuclear scales and dominates the interactions of nucleons (protons or neutrons).
- Possible nuclear reactions are constrained by the law of conservation of nucleon number.
- The behavior of the constituent particles of a nuclear reaction is constrained by laws of conservation of energy, energy-mass equivalence, and conservation of momentum.
- For all nuclear reactions, mass and energy may be exchanged due to mass-energy equivalence. Relevant equation:
- Energy may be released in nuclear processes in the form of kinetic energy of the products or as photons.
- Nuclear fusion is the process by which two or more smaller nuclei combine to form a larger nucleus, as well as subatomic particles.
- Nuclear fission is the process by which the nucleus of an atom splits into two or more smaller nuclei, as well as subatomic particles.
- Nuclear fission may occur spontaneously or may require an energy input, depending on the binding energy of the nucleus.
Describe the radioactive decay of a given sample of material consisting of a finite number of nuclei.
- Radioactive decay is the spontaneous transformation of a nucleus into one or more different nuclei.
- The time at which an individual nucleus undergoes radioactive decay is indeterminable, but decay rates can be described using probability.
- The half-life, t1/2, of a radioactive material is the time it takes for half of the initial number of radioactive nuclei to have spontaneously decayed.
- The decay constant λ can be related to the half-life of a radioactive material with the equation:
- A material’s decay constant may be used to predict the number of nuclei remaining in a sample after a period of time, or the age of a material if the initial amount of material is known. Relevant equation:
- Different unstable elements and isotopes may have vastly different half-lives, ranging from fractions of a second to billions of years.