Glossary

active deposit – the first solid radioelements resulting from the decay of gaseous emanation (radon).

alpha ray / alpha particle – the positively charged radioactive emission, identical to the nucleus of a helium atom, with two protons and two neutrons.

atom – the smallest entity of an individual element, consisting of at least one proton and one electron.

atomic number – the number of protons in an atom.

atomic weight – the combined number of protons and neutrons in an atom.

beta ray / beta particle – the negatively charged radioactive emission, identical to an electron.

compound – two or more elements chemically bound to form a new material, such as water from hydrogen and oxygen.

cosmic ray – a fast-moving charged particle, accelerated by its travels through space, that arrives at Earth and ionizes air molecules in the atmosphere, generating showers of secondary particles.

curie – a unit of measurement in radioactivity.

curiethérapie / curietherapy – the use of radioactivity in medical treatment, primarily for cancer.

cryogenic laboratory – a venue for studying matter at extremely low temperatures.

electrolysis – the process by which a solution is separated into its component ions.

electromagnetic radiation – the full range of light wavelengths, from radio waves through infrared, visible light, ultraviolet, X-rays, and gamma rays.

electron – the negatively charged particle in an atom; the carrier of electric current; the beta emission.

electroscope – a device for assessing electric charge; the earliest ones had a pair of small gold “leaves” that flew apart when a charged object came close.

element – a unique manifestation of matter, ninety-four of which are naturally occurring.

emanation – the original term for radon, the inert gas produced by the radioactive decay of radium, thorium, and actinium.

gamma ray – the electrically neutral and most highly penetrating radioactive emission; a high-energy variation of visible light.

half-life – the time it takes for half of a radioactive sample to decay.

ion – an electrically charged particle.

ionium – a “new element” discovered in 1907 by Bertram Boltwood, later shown to be an isotope of thorium.

ionize – to imbue with electric charge, as by stripping electrons from atoms so that they become positively charged.

isotope – a variant of an element, identical to that element in properties but differing from it in atomic weight.

mesothorium – a “new element” discovered in 1907 by Otto Hahn, later seen as two “new elements,” mesothorium 1 and mesothorium 2, which turned out to be isotopes, respectively, of radium and actinium.

meteorology – the study of the atmosphere, especially weather and climate.

metrology – the science and practice of precise measurement.

molecule – the smallest unit of a compound, or of a diatomic gas such as hydrogen, nitrogen, or oxygen.

neutron – a subatomic particle with about the mass of a proton but without charge.

nucleus – the central region of an atom and the locus of its positive charge.

photon – the smallest unit of visible light or other electromagnetic radiation.

positron – the first anti-matter particle discovered; a positive electron.

proton – the positively charged particle in the nucleus of an atom.

quanta – tiny “packets” or “particles” of energy.

quantum mechanics – the theory and tools of mathematical analysis pertaining to subatomic phenomena.

radioactivity – the spontaneous emission of energy and subatomic particles from the nuclei of certain chemical elements.

radiothorium – an isotope of thorium (Th-228) once thought to be a new element.

salt – a soluble, crystalline chemical compound, often made up of an acid and a base, or a metal and a nonmetal.

spectrum – the wavelengths of light emitted by an element when it is heated to incandescence.