Key Terms

activity

rate of decay for radioactive nuclides

alpha decay

type of radioactive decay in which an atomic nucleus emits an alpha particle

anger camera

common medical imaging device that uses a scintillator connected to a series of photomultipliers

atomic number

number of protons in a nucleus

becquerel

SI unit for rate of decay of a radioactive material

beta decay

type of radioactive decay in which an atomic nucleus emits a beta particle

carbon-14 dating

radioactive dating technique based on the radioactivity of carbon-14

chain reaction

self-sustaining sequence of events, exemplified by the self-sustaining nature of a fission reaction at critical mass

critical mass

minimum amount necessary for self-sustained fission of a given nuclide

decay constant

quantity that is inversely proportional to the half-life and that is used in the equation for number of nuclei as a function of time

energy-level diagram

a diagram used to analyze the energy levels of electrons in the orbits of an atom

excited state

any state beyond the n = 1 orbital in which the electron stores energy

Fraunhofer lines

black lines shown on an absorption spectrum that show the wavelengths absorbed by a gas

gamma decay

type of radioactive decay in which an atomic nucleus emits a gamma ray

Geiger tube

very common radiation detector that usually gives an audio output

ground state

the n=1 orbital of an electron

half-life

time in which there is a 50 percent chance that a nucleus will decay

Heisenberg uncertainty principle

fundamental limit to the precision with which pairs of quantities such as momentum and position can be measured

hydrogen-like atom

any atom with only a single electron

isotope

nuclei having the same Z and different N’s

liquid drop model

model of the atomic nucleus (useful only to understand some of its features) in which nucleons in a nucleus act like atoms in a drop

mass number

number of nucleons in a nucleus

nuclear fission

reaction in which a nucleus splits

nuclear fusion

reaction in which two nuclei are combined, or fused, to form a larger nucleus

nucleons

particles found inside nuclei

planetary model of the atom

model of the atom that shows electrons orbiting like planets about a Sun-like nucleus

proton-proton cycle

combined reactions $${}^{\text{1}}\text{H}{+}^1\text{H} \to { }^2\text{H} + e^{-}+v_e.$$ $${}^{\text{1}}\text{H}{+}^2\text{H} \to { }^3\text{He} + \gamma$$ and $${}^{\text{3}}\text{He}{+}^3\text{He} \to { }^4\text{He} {+}^1\text{H} {+}^1\text{H}$$ that begins with hydrogen and ends with helium

rad

amount of ionizing energy deposited per kilogram of tissue

radioactive

substance or object that emits nuclear radiation

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

process by which an atomic nucleus of an unstable atom loses mass and energy by emitting ionizing particles

radioactivity

emission of rays from the nuclei of atoms

radiopharmaceutical

compound used for medical imaging

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

Rutherford scattering

scattering of alpha particles by gold nuclei in the gold foil experiment

Rydberg constant

a physical constant related to atomic spectra, with an established value of $$1.097\times {10}^7{\text{m}}^{-1}$$

scintillator

radiation detection method that records light produced when radiation interacts with materials

strong nuclear force

attractive force that holds nucleons together within the nucleus

tagged

having a radioactive substance attached (to a chemical compound)

therapeutic ratio

the ratio of abnormal cells killed to normal cells killed

transmutation

process of changing elemental composition