.Activation energy
(Ea) The
minimum amount of energy required for a reaction to occur.
Alpha(a) particle A particle ejected in one form of radioactive decay, identical to the helium-4 nucleus. A common mode of decay for radioactive nuclides in which the mass number changes.
Atomic mass
The averaged mass of the atoms of an element, taking into account the
relative abundance of the various isotopes in a naturally occurring substance.
Also called the atomic weight which is recorded on the Periodic Table.
Atomic mass units
(amu) A unit of mass
defined as 1/12 the mass of a carbon-12 atom; approximately equal to the mass of
one proton or one neutron.
Atomic number (Z) The number of protons in a given element, atom or isotope.
Becquerel (Bq) - A measure that enables us to compare the typical radioactivity of some natural and other materials. A becquerel is one atomic decay per second.
Beta (b) - An electron produced and ejected during radioactive beta decay.
Beta (b) production A decay process for radioactive nuclides in which the mass number remains constant and atomic number changes. The net effect is to change a neutron to a proton.
Binding energy The energy required to break a nucleus apart (decompose) into its constituent neutrons and protons.
Carbon-14 (radiocarbon) dating A technique for
estimating the age of (ancient) objects by measuring the amount of radioactive
carbon-14 remaining. A second
definition states it is based on the rate of radioactive decay of the nuclide
.
Cyclotron- A type of particle accelerator in which an ion introduced at the center is accelerated in an expanding spiral path by the use of alternating electrical fields in the presence of a magnetic field.
Fission The process of using a neutron to split a heavy nucleus into two nuclei with small mass numbers.
Fusion The process of combining two light nuclei to form a heavier, more stable nucleus.
Gamma (g) decay releases energy but does not change A or Z.
Gamma (g) radiation High energy photons often emitted in radioactive decay.
Geiger counter (Geiger-Műller counter) - An instrument used to measure radioactivity or the rate of radioactive decay based on the ions and electrons produced as a radioactive particle passes through a gas-filled chamber.
Half-life The time required for the amount of a reactant to decrease to one-half of its former value.
Isotope Atoms of the same element (the same number of protons) with different number of neutrons. They have identical atomic numbers (Z) but differ in mass numbers (A).
Isotopic Symbol A short hand symbol of an isotope
specifying the mass number (A), atomic number (Z) and element symbol (X)
in the form
.
Mass defect The difference between the sum of the masses of neutrons and protons forming a nucleus and the mass of that nucleus; the mass equivalence of binding energy, with the two related via the equation E=mc2. Note: the mass of a nucleus is always less than the combined masses of its constituent protons and neutrons.
Mass number (A) - The sum of the protons and neutrons of an atom or isotope.
Neutron (N) A subatomic particle contained within the nucleus of an atom. It carries no charge and has a mass very slightly larger than that of a proton.
Nucleon A particle found in the nucleus of an atom; can be either a neutron or a proton.
Nucleus The small central region of an atom; a dense, positively charged area containing protons and neutrons.
Nuclide- The general term applied to each unique atom;
represented by
where X is the symbol for a
particular element.
Particle accelerator- A device used to accelerate nuclear particles to very high speeds.
Photon- A quantum of energy in the form of light with a value of Plancks constant multiplied by the frequency of the light. (E=hn)
Positron An anti-electron: It has the same mass but opposite charge as an electron, and is emitted during a particular form of radioactive decay.
Proton A subatomic particle that carries a single positive charge and has a mass defined as one . The number of protons in an element, atom or isotope is equal to the Atomic Number (Z).
Rad A unit of radiation dosage corresponding to 10-2 J of energy deposited per kilogram of tissue (from radiation absorbed dose).
Radioactive Decay Half-Life (T1/2) The fraction of original nuclei remaining after n half-lives = (½)n. The fraction of nuclei that has decayed away after n half-lives = 1 - (½)n.
Radioactivity- A phenomenon exhibited by certain unstable isotopes in which they undergo spontaneous nuclear transformations via emission of one or more particles.
Radiotracer (aka Tracer) A tracer is a radioactive nuclide, introduced into an organism for diagnostic purposes, whose pathway can be traced by monitoring its radioactivity.
Reactor core The part of a nuclear reactor where the fission reaction takes place.
Rem A unit of radiation dosage that accounts for both the energy of the dose and its effectiveness in causing biological damage (from roentgen equivalent for man).
Scintillation counter An instrument used to measure radioactivity by sensing the flashes of light produced in a substance by the radiation (the amount of fluorescence produced).
Spontaneous process A process that will occur on its own without energy input from the surroundings.
Z Represents the number of protons and is equivalent to the atomic number.
Zone of nuclear stability The area encompassing the stable nuclides on a plot of their positions as a function of the number of protons and the number of neutrons in the nucleus.
A
particular combination of protons and neutrons is called a nuclide.
Nuclides with the same number of protons are called isotopes. Nuclides
with the same mass number are isobars. Nuclides with the same number of
neutrons are isotones.