radioactivity

Alpha (α) Decay

Loss of an alpha particle during radioactive decay.

Alpha Particle

High-energy helium nucleus; a helium atom that has lost two electrons and contains two protons and two neutrons.

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

High-energy electron.

Curie (Ci)

Larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7×10^{10} 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.

Gamma (γ) Emission

Decay of an excited-state nuclide accompanied by emission of a gamma ray.

Gamma Ray

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 (t_{1/2})

Time required for half of the atoms in a radioactive sample to decay.

Ionizing Radiation

Radiation that can cause a molecule to lose an electron and form an ion.

Millicurie (mCi)

Larger unit for rate of radioactive decay frequently used in medicine; 1 mCi = 0.001 Ci = 3.7×10^{7} disintegrations/s.

Nuclear Chemistry

Study of the structure of atomic nuclei and processes that change nuclear structure.

Nuclear Reaction

Change to a nucleus, resulting in changes in the atomic number, mass number, or energy state.

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.

Positron

Antiparticle to the electron; it has identical properties to an electron, except for having the opposite (positive) charge.

Positron Emission (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.

Radioactivity

Phenomenon exhibited by an unstable nucleon that spontaneously undergoes change into a nucleon that is more stable.

Radiocarbon Dating

Highly accurate means of dating objects 30,000–50,000 years old derived from once-living matter.

Radioisotope

Isotope that is unstable and undergoes conversion into a different, more stable isotope.

Sievert (Sv)

SI unit measuring tissue damage caused by radiation; accounts for energy and biological effects.