integrated rate laws Integrated rate laws are used to
relate concentrations and time. The rate law provides
an equation that relates the reaction rate to the concen-
tration of a species in the reaction. The integrated rate
law has a very different form for first-, second-, and
zero-order reactions.
See alsoRATE OF REACTION.
inter- A prefix meaning between or among.
intercalation compounds Compounds resulting
from inclusion, usually without covalent bonding, of
one kind of molecule (the GUESTmolecule) in a matrix
of another compound (the HOSTcompound), which has
a layered structure. The host compound, with a rather
rigid structure, may be macromolecular, crystalline, or
amorphous.
interferon A chemical messenger of the immune sys-
tem, composed of a group of cytokine proteins that
have antiviral characteristics that are capable of help-
ing the immune response. Three main types of inter-
feron—alpha, beta, and gamma—are produced by
virus-infected cells and are released to coat uninfected
cells, thus preventing them from becoming infected.
Alpha interferon is produced by virus-infected mono-
cytes and lymphocytes, while beta is produced by virus-
infected fibroblasts. Gamma is produced by stimulated
T and NK (natural killer) cells.
intermediate A MOLECULAR ENTITYwith a LIFETIME
appreciably longer than a molecular vibration (corre-
sponding to a local potential energy minimum of depth
greater than reagent type) that is formed (directly or
indirectly) from the reactants and reacts further to give
(either directly or indirectly) the products of a chemical
reaction as well as the corresponding CHEMICAL
SPECIES.
See alsoELEMENTARY REACTION; REACTION STEP;
STEPWISE REACTION.
intermolecular (1) Descriptive of any process that
involves a transfer (of atoms, GROUPs, electrons, etc.)
or interactions between two or more MOLECULAR
ENTITIES.
(2) Relating to a comparison between different
molecular entities.
See alsoINTRAMOLECULAR.intermolecular forces Forces of attraction that exist
between particles (atoms, molecules, ions) in a com-
pound.internal conversion Described as an alternative pro-
cess to gamma-ray emission that frequently occurs in
metastable NUCLIDEs. An excited nucleus transfers its
excitation energy to an orbital electron (called the con-
version electron), which is then ejected from the atom.
The excess energy of the electron-binding energy travels
with the electron as kinetic energy. The orbital vacancy
is filled by another shell electron, giving rise to the
emission of characteristic X-rays or Auger electrons.internal energy Energy that is associated with the
random, disordered motion of molecules. The internal
energy of a system is defined as the sum of the energies
of all the constituent particles.internal return SeeION-PAIR RETURN.interstitial One of the three classes of HYDRIDEs:
covalent, interstitial, and ionic. A hydride is a binary
compound containing hydrogen. The hydride ion, H-,
occurs in ionic hydrides. More generally, applied to
solid solutions in which the (small) solute atoms
occupy interstitial positions between the (larger) atoms
of the solvent. Interstitial positions are the spaces that
are empty when spherical particles such as atoms are
packed together. Octahedral and tetrahedral holes are
examples on interstitial sites in close packed lattices.intimate ion pair SeeION PAIR.intra- A prefix meaning within or inside.intra- 141