n: The letter "n" when used as a prefix
before a unit symbol indicates a multiplier of 10-9. Abbreviation of "nano".
E.g., nV = 10-9 volt, one nanovolt, one billionth of a volt.
nA: Symbol and abbreviation of nanoampere
(= 10-9 ampere, one billionth of an ampere).
nano: When used as a prefix before a
unit name it indicates a multiplier of 10-9. E.g., nanovolt = 10-9 volt, one
billionth of a volt. Symbol: "n".
nanoampere: 10-9 ampere,
symbol: "nA" (one billionth of an ampere).
Nanometer: abbreviated "nm", a unit
of length equal to one thousandth of a micrometer.
nanovolt: 10-9 volt, symbol:
"nV" (one billionth of a volt).
Negatively charged electrode, usually of a secondary cell; acts as
anode during discharge and cathode during charge.
Nernst equation: An equation defining
the equilibrium potential of an electrode. The potential is the sum of the standard
electrode potential and a correction term for the deviation from unit concentrations
of the reactant and the product of the electrode reaction in the solution; if
the "reduced" form is a metal, a pure metal (not alloyed with other metals)
is considered to be at unit concentration. The correction term is the product
of the "Nernst slope" and the logarithm of the ratio of the concentrations (strictly
speaking, activities) of the oxidized species and the reduced species. At room
temperature, the Nernst slope is 0.05916 volt divided by the number of electrons
transferred during the reaction. E.g., for a simple metal deposition/dissolution
reaction the slope is 0.05916 for a single charged metal cation, 0.00296 volt
for a double charged ion, etc.
Nernst slope: See Nernst equation. It
is equal to the change of equilibrium electrode potential when the concentration
(strictly speaking, activity) of a species involved in the electrode reaction
changes by ten fold.
Nernstian behavior: An electrode is
said to behave "nernstially" if the equilibrium electrode potential obeys the
Nernst equation when the concentration (strictly speaking, activity) of a species
involved in the electrode reaction changes. Opposite: non-nernstian behavior.
Nernstian (or Nernst's) hypothesis:
See diffusion layer.
Nernstian reaction: See reversible electrode
Neutralization: (1) The reaction of
an acid and a base to form a "neutral" (pH = 7) solution. (2) The removal of
electrical charge to produce a "neutral" (electrically uncharged) particle or
Neutron: See atomic structure.
NHE: Stands for "normal hydrogen electrode,"
which is an alternative name for the standard hydrogen electrode.
Noble metal: A metal that resists oxidation
(corrosion) in air, and therefore retains its metallic luster. Examples are
platinum and gold. These metals have high positive standard electrode potentials
and are the lowest ones on the electromotive series. Contrast with active metal.
Non-aqueous solution: A solution with
the solvent anything but water (e.g., organic or inorganic liquid, molten salt).
Non-faradaic current (density): See
capacitive current (density).
Non-nernstian behavior: An electrode
is said to behave "non-nernstially" if the equilibrium electrode potential does
not obey the Nernst equation when the concentration (strictly speaking, activity)
of a species involved in the electrode reaction changes. Opposite: nernstian
Non-ohmic resistance (behavior): A system
or system element is behaving "non-ohmically" if it does not follow Ohm's law.
That is, the value of the resistance depends on the current or the potential.
Opposite: ohmic behavior. The resistance can be formally defined as the differential
of the potential with respect of the current. In the case of Ohm's law, this
is the constant value of the resistance. In electrochemistry, a typical "non-ohmic"
element is the charge-transfer resistance. The charge-transfer reaction can
be considered a circuit element because it requires a certain amount of overpotential
to force through a current. However, the pertinent relation here is the Tafel
law (at least at relatively large overpotentials), and the differential of the
current (that is the resistance) is a function of the current itself.
Non-polarizable electrode: An electrode
that is not easily polarizable. That is, the potential of the electrode will
not change significantly from its equilibrium potential with the application
of even a large current density. The reason for this behavior is that the electrode
reaction is inherently fast (has a large exchange current density). See also
overpotential. Opposite: polarizable electrode.
Non-rechargeable battery: A battery
in which the chemical reaction system providing the electrical current is not
easily "chemically" reversible. It provides current until all the chemicals
placed in it during manufacture are used up. It is discarded after a single
discharge. Also called "primary" battery or cell. Contrast with rechargeable
battery. This battery always operates as a galvanic cell. Consequently, the
anode is the negative electrode, while the cathode is the positive electrode.
Normal electrode potential: Alternative
name for standard electrode potential.
Normal hydrogen electrode: Alternative
name for standard hydrogen electrode. Abbreviated as "NHE."
Nucleus: See atomic structure.
nV: Symbol and abbreviation of nanovolt
(= 10-9 volt, one billionth of a volt).