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OpenStax Chem 21
This content is available for free at http://cnx.org/content/col11760/1.9
| Term | Definition |
|---|---|
| positron emission | (also, β+ decay) conversion of a proton into a neutron, which remains in the nucleus, and a positron, which is emitted |
| radiation absorbed dose (rad) | SI unit for measuring radiation dose, frequently used in medical applications; 1 rad = 0.01 Gy |
| radiation dosimeter | device that measures ionizing radiation and is used to determine personal radiation exposure |
| radiation therapy | use of high-energy radiation to damage the DNA of cancer cells, which kills them or keeps them from dividing |
| radioactive decay | spontaneous decay of an unstable nuclide into another nuclide |
| radioactive decay series | chains of successive disintegrations (radioactive decays) that ultimately lead to a stable end-product |
| radioactive tracer | (also, radioactive label) radioisotope used to track or follow a substance by monitoring its radioactive emissions |
| radioactivity | phenomenon exhibited by an unstable nucleon that spontaneously undergoes change into a nucleon that is more stable; an unstable nucleon is said to be radioactive |
| radiocarbon dating | highly accurate means of dating objects 30,000–50,000 years old that were derived from once-living matter; achieved by calculating the ratio of 6 14C: 6 12C in the object vs. the ratio of 6 14C: 6 12C in the present-day atmosphere |
| radioisotope | isotope that is unstable and undergoes conversion into a different, more stable isotope |
| radiometric dating | use of radioisotopes and their properties to date the formation of objects such as archeological artifacts, formerly living organisms, or geological formations |
| reactor coolant | assembly used to carry the heat produced by fission in a reactor to an external boiler and turbine where it is transformed into electricity |
| relative biological effectiveness (RBE) | measure of the relative damage done by radiation |
| roentgen equivalent man (rem) | unit for radiation damage, frequently used in medicine; 1 rem = 1 Sv |
| scintillation counter | instrument that uses a scintillator—a material that emits light when excited by ionizing radiation—to detect and measure radiation |
| sievert (Sv) | SI unit measuring tissue damage caused by radiation; takes into account energy and biological effects of radiation |
| strong nuclear force | force of attraction between nucleons that holds a nucleus together |
| subcritical mass | amount of fissionable material that cannot sustain a chain reaction; less than a critical mass |
| supercritical mass | amount of material in which there is an increasing rate of fission |
| transmutation reaction | bombardment of one type of nuclei with other nuclei or neutrons |
| transuranium element | element with an atomic number greater than 92; these elements do not occur in nature |
| gamma ray | (γ or 0 0γ) short wavelength, high-energy electromagnetic radiation that exhibits wave-particle duality |
| Geiger counter | instrument that detects and measures radiation via the ionization produced in a Geiger-Müller tube |
| gray (Gy) | SI unit for measuring radiation dose; 1 Gy = 1 J absorbed/kg tissue |
| half-life (t1/2) | time required for half of the atoms in a radioactive sample to decay |
| internal radiation therapy | (also, brachytherapy) radiation from a radioactive substance introduced into the body to kill cancer cells |
| ionizing radiation | radiation that can cause a molecule to lose an electron and form an ion |
| magic number | nuclei with specific numbers of nucleons that are within the band of stability |
| mass defect | difference between the mass of an atom and the summed mass of its constituent subatomic particles (or the mass “lost” when nucleons are brought together to form a nucleus) |
| mass-energy equivalence equation | Albert Einstein’s relationship showing that mass and energy are equivalent |
| millicurie (mCi) | larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 × 1010 disintegrations/s |
| nonionizing radiation | radiation that speeds up the movement of atoms and molecules; it is equivalent to heating a sample, but is not energetic enough to cause the ionization of molecules |
| nuclear binding energy | energy lost when an atom’s nucleons are bound together (or the energy needed to break a nucleus into its constituent protons and neutrons) |
| nuclear chemistry | study of the structure of atomic nuclei and processes that change nuclear structure |
| nuclear fuel | fissionable isotope present in sufficient quantities to provide a self-sustaining chain reaction in a nuclear reactor |
| nuclear moderator | substance that slows neutrons to a speed low enough to cause fission |
| nuclear reaction | change to a nucleus resulting in changes in the atomic number, mass number, or energy state |
| nuclear reactor | environment that produces energy via nuclear fission in which the chain reaction is controlled and sustained without explosion |
| nuclear transmutation | conversion of one nuclide into another nuclide |
| nucleon | collective term for protons and neutrons in a nucleus |
| nuclide | nucleus of a particular isotope |
| parent nuclide | unstable nuclide that changes spontaneously into another (daughter) nuclide |
| particle accelerator | device that uses electric and magnetic fields to increase the kinetic energy of nuclei used in transmutation reactions |
| positron (+10β or +10 e) | antiparticle to the electron; it has identical properties to an electron, except for having the opposite (positive) charge |
| alpha (α) decay | loss of an alpha particle during radioactive decay |
| alpha particle (α or 24He or 24α) | high-energy helium nucleus; a helium atom that has lost two electrons and contains two protons and two neutrons |
| antimatter | particles with the same mass but opposite properties (such as charge) of ordinary particles |
| band of stability | (also, belt of stability, zone of stability, or valley of stability) region of graph of number of protons versus number of neutrons containing stable (nonradioactive) nuclides |
| becquerel (Bq) | SI unit for rate of radioactive decay; 1 Bq = 1 disintegration/s |
| beta (β) decay | breakdown of a neutron into a proton, which remains in the nucleus, and an electron, which is emitted as a beta particle |
| beta particle (β or −10e or −10β) | high-energy electron |
| binding energy per nucleon | total binding energy for the nucleus divided by the number of nucleons in the nucleus |
| chain reaction | repeated fission caused when the neutrons released in fission bombard other atoms |
| chemotherapy | similar to internal radiation therapy, but chemical rather than radioactive substances are introduced into the body to kill cancer cells |
| containment system | (also, shield) a three-part structure of materials that protects the exterior of a nuclear fission reactor and operating personnel from the high temperatures, pressures, and radiation levels inside the reactor |
| control rod | material inserted into the fuel assembly that absorbs neutrons and can be raised or lowered to adjust the rate of a fission reaction |
| critical mass | amount of fissionable material that will support a self-sustaining (nuclear fission) chain reaction |
| curie (Ci) | larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 × 1010 disintegrations/s |
| daughter nuclide | nuclide produced by the radioactive decay of another nuclide; may be stable or may decay further |
| electron capture | combination of a core electron with a proton to yield a neutron within the nucleus |
| electron volt (eV) | measurement unit of nuclear binding energies, with 1 eV equaling the amount energy due to the moving an electron across an electric potential difference of 1 volt |
| external beam radiation therapy | radiation delivered by a machine outside the body |
| fissile (or fissionable) | when a material is capable of sustaining a nuclear fission reaction |
| fission | splitting of a heavier nucleus into two or more lighter nuclei, usually accompanied by the conversion of mass into large amounts of energy |
| fusion | combination of very light nuclei into heavier nuclei, accompanied by the conversion of mass into large amounts of energy |
| fusion reactor | nuclear reactor in which fusion reactions of light nuclei are controlled |
| gamma (γ) emission | decay of an excited-state nuclide accompanied by emission of a gamma ray |
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