The Foundations of Chemistry

(Marcin) #1

1034 CHAPTER 26: Nuclear Chemistry


Key Terms


Alpha particle ( ) A particle that consists of two protons and
two neutrons; identical to a helium nucleus.
Artificial transmutation An artificially induced nuclear reaction
caused by bombardment of a nucleus with subatomic particles
or small nuclei.


Band of stability A band containing stable (nonradioactive)
nuclides in a plot of number of neutrons versus number of pro-
tons (atomic number).


Beta particle () An electron emitted from the nucleus when a
neutron decays to a proton and an electron.
Binding energy (nuclear binding energy) The energy equiva-
lent (Emc^2 ) of the mass deficiency of an atom.


Breeder reactor A fission reactor that produces more fission-
able material than it consumes.
Chain reaction A reaction that, once initiated, sustains itself and
expands.


Cloud chamber A device for observing the paths of speeding
particles as vapor molecules condense on the ionized air mol-
ecules in their tracks.


Control rods Rods of materials such as cadmium or boron steel
that act as neutron absorbers (not merely moderators), used in
nuclear reactors to control neutron fluxes and therefore rates
of fission.
Critical mass The minimum mass of a particular fissionable
nuclide, in a given volume, that is required to sustain a nuclear
chain reaction.


Cyclotron A device for accelerating charged particles along a
spiral path.


Daughter nuclide A nuclide that is produced in a nuclear decay.
Electron capture Absorption of an electron from the first
energy level (Kshell) by a proton as it is converted to a neu-
tron; also Kcapture.


Fast neutron A neutron ejected at high kinetic energy in a
nuclear reaction.
Fluorescence Absorption of high-energy radiation by a sub-
stance and the subsequent emission of visible light.


Gamma ray () High-energy electromagnetic radiation.


Geiger-Müller counter A type of gas ionization counter used
to detect radiation.
Half-life of a radionuclide The time required for half of a given
sample to undergo radioactive decay.


Heavy water Water containing deuterium, a heavy isotope of
hydrogen,^21 H.
Linear accelerator A device used for accelerating charged par-
ticles along a straight-line path.


Mass deficiency The amount of matter that would be con-
verted into energy if an atom were formed from constituent
particles.


Moderator A substance such as hydrogen, deuterium, oxygen,
or paraffin capable of slowing fast neutrons upon collision.
Nuclear binding energy The energy equivalent of the mass
deficiency; energy released in the formation of an atom from
subatomic particles.
Nuclear fission The process in which a heavy nucleus splits into
nuclei of intermediate masses and one or more neutrons are
emitted.
Nuclear fusion The combination of light nuclei to produce a
heavier nucleus.
Nuclear reaction A reaction involving a change in the compo-
sition of a nucleus; it can evolve or absorb an extraordinarily
large amount of energy.
Nuclear reactor A system in which controlled nuclear fission
reactions generate heat energy on a large scale. The heat energy
is subsequently converted into electrical energy.
Nucleons Particles comprising the nucleus; protons and neu-
trons.
Nuclides Different atomic forms of all elements (in contrast to
isotopes, which are different atomic forms of a single element).
Parent nuclide A nuclide that undergoes nuclear decay.
Plasma A physical state of matter that exists at extremely high
temperatures, in which all molecules are dissociated and most
atoms are ionized.
Positron A nuclear particle with the mass of an electron but
opposite charge.
Radiation High-energy particles or rays emitted in nuclear decay
processes.
Radioactive dating A method of dating ancient objects by deter-
mining the ratio of amounts of a parent nuclide and one of its
decay products present in an object and relating the ratio to the
object’s age via half-life calculations.
Radioactive tracer A small amount of radioisotope that replaces
a nonradioactive isotope of the element in a compound whose
path (e.g., in the body) or whose decomposition products are
to be monitored by detection of radioactivity; also called a
radioactive label.
Radioactivity The spontaneous disintegration of atomic nuclei.
Radioisotope A radioactive isotope of an element.
Radionuclide A radioactive nuclide.
Scintillation counter A device used for the quantitative detec-
tion of radiation.
Slow neutron A fast neutron slowed by collision with a moder-
ator.
Thermonuclear energy Energy from nuclear fusion reactions.
Transuranium elements The elements with atomic numbers
greater than 92 (uranium); none occurs naturally and all must
be prepared by nuclear bombardment of other elements.
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