Key Terms

Key Terms

activity

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

antielectrons

another term for positrons

antineutrino

antiparticle of an electron’s neutrino in ${\beta }^{-}$ 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 $1\text{u}=1.66054\times {10}^{\mathrm{-27}}\text{kg}$

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 ($\beta$) 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 ${}^{14}\text{C/}{}^{12}\text{C}$

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

criticality

condition in which a chain reaction easily becomes self-sustaining

curie (Ci)

unit of decay rate, or the activity of 1 g of ${}^{226}\text{Ra}$, equal to $3.70\times {10}^{10}\text{Bq}$

daughter nucleus

nucleus produced by the decay of a parent nucleus

decay

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

fission

splitting of a nucleus

gamma ($\gamma$) 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

half-life

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)

isotopes

nuclei having the same number of protons but different numbers of neutrons

lifetime

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)

neutrino

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

nucleons

protons and neutrons found inside the nucleus of an atom

nucleosynthesis

process of fusion by which all elements on Earth are believed to have been created

nuclide

nucleus

parent nucleus

original nucleus before decay

positron

electron with positive charge

positron emission tomography (PET)

tomography technique that uses ${\beta }^{+}$ emitters and detects the two annihilation $\gamma$ 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

radioactivity

spontaneous emission of radiation from nuclei

radiopharmaceutical

compound used for medical imaging

radius of a nucleus

radius of a nucleus is defined as $r=r_0{A}^{1\text{/}3}$

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 $\gamma$-emitting radiopharmaceuticals

strong nuclear force

force that binds nucleons together in the nucleus

transuranic element

element that lies beyond uranium in the periodic table