gamma-radiation that produces ion
pairs carrying 1 coulomb of charge of
either sign in 1 kilogram of pure dry
air. The former unit, the roentgen
(R), is equal to 2.58 × 10 –4Ckg–1.radiative capture See capture.
radicalA group of atoms, either in
a compound or existing alone. See
free radical; functional group.
A- Information about IUPAC nomenclature
- List of radical names
radical ionA radical that has a pos-
itive or negative charge. An example
is the benzene radical cation C 6 H 6 .+.
In radical ions, the odd electron and
the charge are usually (but not neces-
sarily) on the same atom.
radioactive ageThe age of an ar-
chaeological or geological specimen
as determined by a process that de-
pends on a radioactive decay. See car-
bon dating; fission-track dating;
potassium–argon dating; rubidium–
strontium dating; uranium–lead
dating.radioactive datingSee radiomet-
ric dating.
radioactive isotopeSee radioiso-
tope.radioactive nuclideSee radionu-
clide.radioactive seriesA series of
radioactive nuclides in which each
member of the series is formed by
the decay of the nuclide before it.
The series ends with a stable nuclide.
Three radioactive series occur natu-
rally, those headed by thorium–232
(thorium series), uranium–235 (ac-
tinium series), and uranium–238 (ura-
nium series). All three series end with
an isotope of lead. The neptunium se-
riesstarts with the artiÜcial isotope
plutonium–241, which decays to nep-tunium–237, and ends with bis-
muth–209.radioactive tracingSee labelling.
radioactivityThe spontaneous dis-
integration of certain atomic nuclei
accompanied by the emission of
alpha-particles (helium nuclei), beta-
particles (electrons or positrons), or
gamma radiation (short-wavelength
electromagnetic waves).
Natural radioactivity is the result of
the spontaneous disintegration of
naturally occurring radioisotopes.
Many radioisotopes can be arranged
in three *radioactive series. The rate
of disintegration is uninÛuenced by
chemical changes or any normal
changes in their environment. How-
ever, radioactivity can be induced in
many nuclides by bombarding them
with neutrons or other particles. See
also decay; ionizing radiation; radi-
ation units.radiocarbon datingSee carbon
dating.radiochemistryThe branch of
chemistry concerned with radio-
active compounds and with ioni-
zation. It includes the study of
compounds of radioactive elements
and the preparation and use of com-
pounds containing radioactive atoms.
See labelling; radiolysis.radiogenicResulting from radio-
active decay.
radioimmunoassay(RIA)A sensi-
tive quantitative method for detect-
ing trace amounts of a biomolecule,
based on its capacity to displace a ra-
dioactively labelled form of the mol-
ecule from combination with its
antibody.
radioisotope(radioactive isotope)
An isotope of an element that is
radioactive. See labelling.radiolysisThe use of ionizing radi-radiative capture 452r