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Key Terms

magnitude of the decay rate for radioactive nuclides
alpha (α) rays
one of the types of rays emitted from the nucleus of an atom as alpha particles
alpha decay
radioactive nuclear decay associated with the emission of an alpha particle
another term for positrons
antiparticle of an electron’s neutrino in ββ decay
atomic mass
total mass of the protons, neutrons, and electrons in a single atom
atomic mass unit
unit used to express the mass of an individual nucleus, where 1u=1.66054×10−27kg1u=1.66054×10−27kg
atomic nucleus
tightly packed group of nucleons at the center of an atom
atomic number
number of protons in a nucleus
becquerel (Bq)
SI unit for the decay rate of a radioactive material, equal to 1 decay/second
beta (ββ) rays
one of the types of rays emitted from the nucleus of an atom as beta particles
beta decay
radioactive nuclear decay associated with the emission of a beta particle
binding energy (BE)
energy needed to break a nucleus into its constituent protons and neutrons
binding energy per nucleon (BEN)
energy need to remove a nucleon from a nucleus
breeder reactor
reactor that is designed to make plutonium
carbon-14 dating
method to determine the age of formerly living tissue using the ratio 14C/12C14C/12C
chart of the nuclides
graph comprising stable and unstable nuclei
critical mass
minimum mass required of a given nuclide in order for self-sustained fission to occur
condition in which a chain reaction easily becomes self-sustaining
curie (Ci)
unit of decay rate, or the activity of 1 g of 226Ra226Ra, equal to 3.70×1010Bq3.70×1010Bq
daughter nucleus
nucleus produced by the decay of a parent nucleus
process by which an individual atomic nucleus of an unstable atom loses mass and energy by emitting ionizing particles
decay constant
quantity that is inversely proportional to the half-life and that is used in equation for number of nuclei as a function of time
decay series
series of nuclear decays ending in a stable nucleus
splitting of a nucleus
gamma (γγ) rays
one of the types of rays emitted from the nucleus of an atom as gamma particles
gamma decay
radioactive nuclear decay associated with the emission of gamma radiation
time for half of the original nuclei to decay (or half of the original nuclei remain)
high dose
dose of radiation greater than 1 Sv (100 rem)
nuclei having the same number of protons but different numbers of neutrons
average time that a nucleus exists before decaying
liquid drop model
model of nucleus (only to understand some of its features) in which nucleons in a nucleus act like atoms in a drop
low dose
dose of radiation less than 100 mSv (10 rem)
mass defect
difference between the mass of a nucleus and the total mass of its constituent nucleons
mass number
number of nucleons in a nucleus
moderate dose
dose of radiation from 0.1 Sv to 1 Sv (10 to 100 rem)
subatomic elementary particle which has no net electric charge
neutron number
number of neutrons in a nucleus
nuclear fusion
process of combining lighter nuclei to make heavier nuclei
nuclear fusion reactor
nuclear reactor that uses the fusion chain to produce energy
protons and neutrons found inside the nucleus of an atom
process of fusion by which all elements on Earth are believed to have been created
parent nucleus
original nucleus before decay
electron with positive charge
positron emission tomography (PET)
tomography technique that uses β+β+ emitters and detects the two annihilation γγ rays, aiding in source localization
proton-proton chain
combined reactions that fuse hydrogen nuclei to produce He nuclei
radiation dose unit (rad)
ionizing energy deposited per kilogram of tissue
radioactive dating
application of radioactive decay in which the age of a material is determined by the amount of radioactivity of a particular type that occurs
radioactive decay law
describes the exponential decrease of parent nuclei in a radioactive sample
radioactive tags
special drugs (radiopharmaceuticals) that allow doctors to track movement of other drugs in the body
spontaneous emission of radiation from nuclei
compound used for medical imaging
radius of a nucleus
radius of a nucleus is defined as r=r0A1/3r=r0A1/3
relative biological effectiveness (RBE)
number that expresses the relative amount of damage that a fixed amount of ionizing radiation of a given type can inflict on biological tissues
roentgen equivalent man (rem)
dose unit more closely related to effects in biological tissue
sievert (Sv)
SI equivalent of the rem
single-photon-emission computed tomography (SPECT)
tomography performed with γγ-emitting radiopharmaceuticals
strong nuclear force
force that binds nucleons together in the nucleus
transuranic element
element that lies beyond uranium in the periodic table
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