ideal gas A hypothetical gas that appears to obey
perfectly the ideal gas law as the pressure nears zero;
a gas characterized by a complete absence of cohe-
sive forces between molecules; no gas has met this
requirement.
ideal gas law A gas that conforms in its physical
behavior to an idealized relation between pressure, vol-
ume, and temperature.
ideal solution A solution where each component
behaves independently of other components; solvent-
solvent and solvent-solute interactions are the same.
identity reaction A CHEMICAL REACTION whose
products are chemically identical with the reactants,
e.g., the bimolecular self exchange reaction of CH 3 I
with I–.
See alsoDEGENERATE REARRANGEMENT.
igneous rock Formed by the cooling and crystalliza-
tion of molten rock. The term is derived from ignius,
the Latin word for fire.
imaging A medical diagnostic technique by which
useful organ images are obtained from the radiation
emitted by RADIONUCLIDEs that are introduced into
organs, or from radiation absorbed by atomic nuclei
within the organs. Typical examples are imaging
obtained by recording the radiation emitted by a
radionuclide such as 99mT c and the^1 H-NMR imaging
obtained by whole-body NUCLEAR MAGNETIC RESO-
NANCEmeasurements.
See also BONE IMAGING; BRAIN IMAGING; MAG-
NETIC RESONANCE IMAGING.imbalance The situation in which REACTIONparam-
eters that characterize different bond-forming or
bond-breaking processes in the same reaction have
developed to different extents as the TRANSITION
STATE is approached along some arbitrarily defined
reaction coordinate. For example, in the nitroalkane
anomaly, the Bronstedβexponent for proton removal
is smaller than the Bronstedα for the nitroalkane
because of imbalance between the amount of bond
breaking and resonance delocalization in the transi-
tion state. Imbalance is common in elimination, addi-
tion, and other complex reactions that involve proton
(hydron) transfer.
See alsoSYNCHRONIZATION; SYNCHRONOUS.imene SeeNITRENE.imidogen SeeNITRENE.137