Theory of Radioactivity Flashcards
What is the rest mass of a proton?
1.00727 u
What is the rest mass of a neutron?
1.00866 u
Graph the stability of a nucleus.
Graph the Binding Energy per Nucleon (MeV) vs. the Mass Number (A).
State the general equation for alpha (α) decay and give one example (Ra-226).
Most alpha emitters have between 4 - 6 MeV of energy.
State the general equation for beta (β-) decay and give one example (H-3).
State the general equation for beta (β+) decay and give one example (Na-22).
Compare the energy spectra for both alpha and beta decays.
- Alpha decays are monoenergetic and produce one energy of alpha particle.
- Beta decay produces a spectrum of beta energies up to a maximum energy (Emax) with the average energy (Eavg) equal to 1/3 of the Emax.
State the general equation for gamma-ray (γ) emission (decay) and give one example (Ba-137*).
Most radioactive nuclides with Z < 82 decay by either __________ or ___________ decay.
Most radioactive nuclides with Z < 82 decay by either Beta or Positron decay.
What are the three types of fission decay?
- Thermal neutron absorption
- Fast fission
- Spontaneous fission
What happens during fast fission?
A nuclide captures a high energy or fast neutron. The resultant nuclide is unstable and decays by separating into two pieces called fission fragments.
Nuclides able to undergo fast fission by capturing a high energy or fast neutron are referred to as _______________.
Nuclides able to undergo fast fission by capturing a high energy or fast neutron are referred to as fissionable.
What happens during spontaneous fission?
What is a common nuclide capable of undergoing spontaneous fission?
A nuclide is able to decay by fissioning without capturing a neutron.
Californium-252 (Cf-252), with a half-life of 2.6 years, is commonly used in calibrating neutron survey meters and personnel radiation dosimeters, as well as treating solid tumors.
State the general equation for electron (e-) capture and give one example (Cr-51).
Occurs in neutron deficient nuclei.
Nuclides deficient in neutrons like to convert one of their protons into a neutron (by capturing a K-shell electron) to become “less deficient.”
State the general equation for internal conversion and give one example (Hg-198*).
Instead of the excited nucleus using its extra energy to produce and release a gamma-ray, it transfers the decay energy to an orbtial electron (usually a K-shell electron).
Since this electron is bound to the nucleus by the Coulomb force, it “uses up” an amount of energy called the electron binding energy to escape the atom.
Define the situation that creates Transient Equilibrium (case 2).
The parent has a slightly larger half-life than the daughter (usually the same order of magnitude).
λD > λP
Define
Isotope
Atoms with the same number of protons.
Define
Isotone
Atoms with the same number of neutrons.
Graph
Activity vs. Time for secular equilibrium (case 1).
Graph
Activity vs. Time for transient equilibrium (case 2).
Why do heavy nuclei have an N-value approximately 1.5 times the Z-value?
- Protons all carry a positive charge and will strongly repel each other according to Coulomb’s Law (when forced together in the nucleus).
- This highly disruptive force is overcome in stable nuclei by the presence of a force even strong than the Coulomb Force called the Nuclear Force.
- By adding relatively more neutrons than protons, additional “glue” is added to heavy nuclei without causing more instability by adding more positive charge.
List
Fundamental forces of nature
- Gravitational ⇒ Long range
- Electromagnetic ⇒ Long range
- Strong nuclear ⇒ Short range
- Weak nuclear ⇒ Short range
