to one newton (1 N) of force applied over an area of
one meter squared (1 m^2 ).
passivation Describes the state where metals or
other materials remain indefinitely unattacked because
of modified or altered surface conditions, although it
has conditions of thermodynamic instability. Also
refers to a commercial process for protection of metals
by creating an inert oxide layer, e.g., the dipping of
steel fittings into a nitric acid solution to rapidly form
a chromium oxide layer on the surface of the material,
thus creating a passive film that protects the metal
from further oxidation.
passive transport A molecule or ion that crosses a
biological membrane by moving down a CONCENTRA-
TIONor ELECTROCHEMICAL GRADIENTwith no expen-
diture of metabolic energy. Passive transport, in the
same direction as a concentration gradient, can occur
spontaneously, or proteins can mediate passive trans-
port and provide the pathway for this movement across
the lipid bilayer without the need to supply energy for
the action. These proteins are called channels if they
mediate ions and permeases for large molecules. This
type of transport always operates from regions of
greater concentration to regions of lesser concentra-
tion. Also called DIFFUSION.
See alsoACTIVE TRANSPORT.
pattern recognition The identification of patterns in
large data sets using appropriate mathematical method-
ologies.
Pauli exclusion principle States that no two elec-
trons in the same atom may have identical sets of four
quantum numbers. Introduced by Austrian-American
physicist Wolfgang Pauli in 1925.
Pauling, Linus (1901–1994) American Chemist
Linus Carl Pauling was born in Portland, Oregon, on
February 28, 1901, to druggist Herman Henry William
Pauling and Lucy Isabelle Darling. He attended the
public elementary and high schools in the town of Con-
don and in Portland, Oregon, and entered the Oregon
State College in 1917. He received a B.Sc. in chemical
engineering in 1922. Pauling married Ava Helen Miller
of Beaver Creek, Oregon, in 1923, and they had four
children. Between 1919 and 1920 he taught quantita-
tive analysis in the state college, later becoming
appointed a teaching fellow in chemistry in the Califor-
nia Institute of Technology. He became a graduate stu-
dent there from 1922 to 1925 and received his Ph.D.
(summa cum laude) in chemistry, with minors in
physics and mathematics.
Like Robert Mulliken, he was inspired by the works
of IRVINGLANGMUIR. In 1919 his interest lay in the field
of molecular structure and the nature of the chemical
bond.
Pauling was a controversial figure much of his life,
but he made important discoveries in physical, struc-
tural, analytical, inorganic, and organic chemistry as
well as biochemistry, combining theoretical physics,
notably quantum theory and quantum mechanics, in
his studies.
He wrote more than 1,000 articles and books for
the field and for the general public—on science, peace,
and health—with such popular books as Vitamin C
and the Common Cold; Cancer and Vitamin C(with
Ewan Cameron, M.D.); and How to Live Longer and
Feel Better.His landmark book The Nature of the
Chemical Bondhas been called one of the most influ-
ential scientific books of the 20th century. His intro-
ductory textbook, General Chemistry,revised several
times since its first printing in 1947 (translated into 13
languages), has been used by generations of undergrad-
uates. He is also often considered the founding father
of molecular biology.
In 1954 he was awarded the Nobel Prize in chem-
istry “for his research into the nature of the chemical
bond and its application to the elucidation of the struc-
ture of complex substances,” and in 1962 he received
the Nobel Peace Prize, the only person to win two such
prizes singularly. He received other awards too numer-
ous to mention.
He died on August 19, 1994, at age 93, at his
ranch near Big Sur, on the California coast.p-block element Elements in Group III to Group
VIII , where the porbitals are being filled.208 passivation