electromagnetic wave Method of travel for radiant
energy (all energy is both particles and waves), so called
because radiant energy has both magnetic and electrical
properties. Electromagnetic waves are produced when
electric charges change their motion. Whether the fre-
quency is high or low, all electromagnetic waves travel at
186,000 miles (300,000 km) per second.
electromeric effect A molecular polarizability effect
occurring by an INTRAMOLECULARelectron displace-
ment (sometimes called the CONJUGATIVE MECHANISM
and, previously, the “tautomeric mechanism”) charac-
terized by the substitution of one electron pair for
another within the same atomic octet of electrons. It
can be indicated by curved arrows symbolizing the dis-
placement of electron pairs, as in
that represents the hypothetical electron shift
The term has been deemed obsolescent or even
obsolete (seeMESOMERIC EFFECT, RESONANCE EFFECT).
Many have used phrases such as “enhanced substituent
resonance effect” that imply the operation of the elec-
tromeric effect without using the term, and various
modern theoretical treatments parametrize the response
of substituents to “electronic demand,” which amounts
to considering the electromeric effect together with the
INDUCTOMERIC EFFECT.
electron A negatively charged subatomic particle of
an atom or ion that is outside of the nucleus. A neutral
atom contains the same number of electrons as there
are protons in the nucleus. A negatively charged BETA
PARTICLEis an electron that is emitted from the nucleus
as a result of a nuclear decay process.
electron acceptor A substance that receives electrons
in an oxidation–reduction reaction.
electron affinity The energy released when an addi-
tional electron (without excess energy) attaches itself to
a MOLECULAR ENTITY(usually an electrically neutral
molecular entity, but also used with single atomic
species). The direct measurement of this quantity
involves molecular entities in the gas phase.electronation SeeELECTRON ATTACHMENT; REDUC-
TION.electron attachment The transfer of an electron to a
MOLECULAR ENTITY, resulting in a molecular entity of
(algebraically) increased negative charge.See alsoOXIDATION(1); REDUCTION.electron capture When one of the inner-orbital elec-
trons in an atom is captured by the nucleus. In the
nucleus, the captured electron reacts with a proton to
produce a neutron, changing the element to one of
lower atomic number.electron configuration SeeCONFIGURATION (ELEC-
TRONIC).electron-deficient bond A single bond between
adjacent atoms that is formed by less than two elec-
trons, as in B 2 H 6 :The B–H–B bonds are called “two-electron three-
center bonds.”electron-deficient bond 91