| A | B |
|---|
| nucleons | a proton or neutron making up a nucleus |
| mass number | the number of nucleons in a nucleus |
| atomic number | the number of protons in a nucleus (also known as the proton number) |
| emission spectrum | the light an element emits; the freqencies emitted are particular to the element in question |
| absoprtion spectrum | the particular requencies absorbed by an element when exposed to a continuous spectrum of light |
| isotopes | nuclei with the same atomic number but different mass number due to a different number of neutrons |
| strong nuclear force | the attractive force between nucleons in a nucleus that keeps them togehter and overcomes the electrical force of repulsion between the protons; has a very short range |
| weak nuclear force | the short-range force acting within the nucleus that is responsible for beta decay |
| Radioactive Decay Law | the rate of decay is proportional to the number of radioactive nuclei present |
| activity | the number of decays per second of a radioactive sample |
| decay constant | the probability of decay per unit time of a given nucleus |
| alpha particle | a helium-4 nucleus emitted in the radioactive decay of certain nuclei (alpha decay) |
| beta particle | an electron or positron emitted in the radioactive decay of certain nuclei (beta decay) |
| gamma ray | a short-wavelength photon emitted in the radioactive decay of certain nuclei (gamma decay) |
| half life | the time after which the activity of a radioactive sample decreases by a factor of two |
| mass defect | the difference between the mass of a nuclues and the sum of the masses of its component nucleons |
| binding energy | the minimum energy required to separate a nucleus into free, unbound nucleons |
| nuclear fusion | the joing of two light nuclei (ligher than nickel) into a larger nucleus plus radiation and energy |
| nuclear fission | the splitting of a large nucleus (heavier than nickel) into two smaller ones plus neutrons, radiation, and energy |
| photon | a zero-rest-mass neutral particle, the quantum of electromagnetic radiation |
| chain reaction | occurs when a fission reaction results in further self sustaining fission reaction |
| critical mass | the minimum mass of uranium-235 that must be present to sustain a chain reaction |
| threshold frequency | the lowest requency of incident electromagnetic radiation that results in electrons being emitted form a metal |
| work function | the minimum energy required to eject an electron from a metal |
| uncertainty principle | a fundamental principle of physics that states that it is impossible to measure simultaneously the momentum and the position of a particle with infinite precision |
