Q
“Qiana” [Du Pont]. TM for a nylon-type syn- quantum number. The quantum is the basic
thetic fiber with properties similar to silk. unit of electromagnetic energy.It characterizes the
wave properties of electrons, as distinct from their
particulate properties. The quantum theory devel-
Q-lure. See cue-lure.
oped by Max Planck states that the energy associ-
ated with any quantum is proportional to the fre-
quad. An energy unit that has come into use in
quency of the radiation, that is e (energy)
=
h!GKu,
recent years in predicting future energy require-
where !GKu is the frequency and h is a universal
ments on a national basis. One quad equals 10
15
Btu,
constant.
which is the energy equivalent of 10
12
cu ft natural
An electron has four quantum numbers that define
gas, or 182 million barrels of oil, or 42 million tons
its properties. These are as follows: (1) The principal
of coal, or 293 billion kilowatt-hours of electricity.
quantum number is a constant that can be any posi-
tive integer (n
=
1, 2, 3 ...). It determines the principal
quadruple point. The temperature at which
energy level, or shell, of the electron, sometimes
four phases are in equilibrium, such as ice, saturated
designated by letters such as K, L, or M, depending
salt solution, water vapor, and salt.
on the value of the principal quantum number. (2)
The angular momentum constant l, also an integer, is
quadrupole resonance. See nuclear quadru-
related to n as l
=
0, 1, ..., n−) 1. Here again, letter
pole resonance.
designations are often used. In s electrons, l
=
0; in p
electrons, l
=
1; in d electrons, l
=
2; and in f elec-
qualitative analysis. See analytical chem-
trons, l
=
3. (3) The magnetic quantum number, m,is
istry.
an integer related to l as: m
=
−1, ..., −1, 0, +1, ..., +l.
(4) The spin quantum number is independent of the
quantitative analysis. See analytical chem-
other three and has a value of either +1/2 or −1/2,
istry.
depending on the direction of rotation of the electron
on its axis in the atomic frame of reference. See
orbital theory; electron; photon; radiation; Pauli
quantization of energy. The assumption that
exclusion principle.
the energy of a particle is not infinitely variable but
can have any one of a definite set of values.
quantum number, azimuthal. The quantum
number specifying the angular momentum of an
quantum dot. (Qdots). Nanometer sized semi-
orbital electron.
conductor particles, made of cadmium selenide
(CdSe), cadmium sulfide (CdS), or cadmium tellu-
quantum number, magnetic. The determi-
ride (CdTe) with an inert polymer coating..
nant of the component of angular momentum vector
of an atomic electron or group of electrons along the
quantum efficiency. (photochemical yield).
externally applied magnetic field.
The number of electrons actually ejected per quan-
tum of light absorbed.
quantum number, radial. The radial motion
quantum number that is an integer for any permitted
quantum jump. See quantum transition.
stationary condition of a particle moving under the
influence of a central field.
quantum mechanics. Quantum mechanics de-
scribes a system of particles in terms of a wave
quantum state. (energy level). The energy
function defined over the configuration space of the
state of an atom as determined by the frequencies of
system. Although the concept of particles having
its characteristic spectral lines.
distinct locations is implicit in the potential energy
function that determines the wave function (e.g., of a
quantum transition. (quantum jump). The
ground-state system), the observable dynamics of
sharp change in an atom accompanied by emission
the system cannot be described in terms of the mo-
or absorption of a quantum of radiant energy.
tion of such particles from point to point. In describ-
ing the energies, distributions, and behaviors of
quantum yield. Number of photon-induced re-
electrons in nanometer-scale structures, quantum
actions of a specified type per photon absorbed.
mechanical methods are necessary. Electron wave
functions help determine the potential energy sur-
face of a molecular system, which in turn is the basis
quark. The smallest known bit of matter. Hypo-
for classical descriptions of molecular motion. thetical entities carrying electrical charges of one-
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