Nuclear Physics Flashcards
in the alpha particle scattering experiment, alpha particles are directed towards a thin gold film. most pass through with very little deviation, but about 1 in 8000 is deviated through an angle greater than 90’. What do these observations provide evidence for?
The nuclei occupy very small volumes within atoms (i think because the a-particles scatter with large angle only when its hitting straight on / v near the nuclei of the atom and gets repelled backwards kinda)
what is an isotope? ew sec 4 chem qn
It is one of two or more atoms with the same atomic number but with different number of neutrons
what is the mass defect?
it is the amount by which the mass of an atomic nucleus is less than the sum of the masses of its constituent particles.
what is the formula for mass defect?
sum of masses of nucleon - mass of nucleus
what is the binding energy of a nucleus?
it is the amount of energy that is required to break a nucleus into its constituent nucleons (i.e. protons and neutrons)
what is the formula for binding energy?
BE = (Δm)c^2
what are the most stable nuclides that we need to know?
Iron-56 / Fe-56 (8.8MeV slightly to the right of the peak)
Nickel-62 / Ni-62 (is at the peak)
for the binding energy per nucleon against mass number graph, which side of the graph do the nuclei undergo fusion and fission?
the left side of the peak undergoes FUSION (to become heavier and reach the stable nuclide)
the right side of the peak undergoes FISSION (to become lighter and reach the stable nuclide)
how to calculate energy released in fusion/fission?
method 1:
E = (mass of reactants - mass of products) c^2
method 2:
E = BE product - BE reactant
when do radioactive decay occur?
it occurs when an unstable nucleus emits an alpha or beta particle or a gamma ray. in the process, the nucleus is transformed into a different and more stable nuclide. this decay is spontaneous and random.
what does it mean when the radioactive decay is spontaneous?
The nucleus decays because it is unstable. it is not triggered or affected by external conditions (temperature, pressure, etc)
what does it mean when the radioactive decay is random?
It is impossible to predict which nucleus will decay at a particular instant or when a particular nucleus will decay.
what is a count rate?
it is a measure of the rate of radiation received by a radioactivity detector assuming that every ionising radiation triggers one count on the ratemeter.
!! count rate -> radiation DETECTED; activity -> ACUTAL NUMBER of disintegrations !!
why on the count rate against time graph, there are irregular fluctuations?
the fluctuation is an indication of the random nature of radioactive decay
what is a background radiation?
the radiation detected by a radiation counter when no radioactive source is nearby
