to his death he was director of the
Pasteur Institute. In 1848 he discovered *optical activity, in 1860 relating it to molecular structure. In 1856
he began work on fermentation, and
by 1862 was able to disprove the existence of spontaneous generation. He
introduced pasteurization (originally
for wine) in 1863. He went on to
study disease and developed vaccines
against cholera (1880), anthrax
(1882), and rabies (1885).
Patterson function A function,
denoted P(x,y,z), used in the analysis
of the results of *X-ray crystallography. P(x,y,z) is deÜned by
P(x,y,z) = Σ
hkl
|F hkl |cos2π(hx + ky + lz),
where h, k, and l are the Miller indices of the crystal. This function is
plotted as a contour map with maxima of the contours at vector distances from the origin, i.e. vectors
from the origin to the point (x,y,z),
where the maximum occurs, corresponding to vector distances between
pairs of maxima in electron density.
Thus, the Patterson function enables
interatomic vectors, which give the
lengths and directions between
atomic centres, to be determined.
This technique, introduced by A. L.
Patterson in 1934, is called Patterson
synthesis and is most useful if the
unit cell contains heavy atoms.
Patterson synthesis See patterson function.
Pauli, Wolfgang Ernst (1900–58)
Austrian-born Swiss physicist. After
studying with Niels *Bohr and Max
*Born, he taught at Heidelberg and,
Ünally Zurich. His formulation in
1924 of the *Pauli exclusion principle explained the electronic make-up
of atoms. For this work he was
awarded the 1945 Nobel Prize for
physics. In 1931 he predicted the existence of the neutrino.
Pauli exclusion principle The
principle that no two electrons in an
atom can have all four quantum
numbers the same. It was Ürst formulated in 1925 by Wolfgang *Pauli and
more generally applies to the quantum states of all elementary particles
with half-integral spin.
Pauling, Linus Carl (1901–94) US
chemist. After spending two years in
Europe, he became a professor at the
Californian Institute of Technology.
His original work was on chemical
bonding; in the mid-1930s he turned
to the structure of proteins, for
which he was awarded the 1954
Nobel Prize for chemistry. He was
also an active campaigner against nuclear weapons and in 1962 was
awarded the Nobel Peace Prize.
Pauling’s rules A set of rules that
enables the structures of many complex ionic crystals to be understood.
These rules involve the sizes and
electrical charges of the ions and
were proposed by Linus *Pauling in
1929. They work well for mainly
ionic crystals, such as silicates, but
less well for crystals, such as sulphides, in which the bonding is
mainly covalent. Pauling put forward
his rules on the basis of empirical observations and calculations of crystal
energies. A number of extensions and
modiÜcations have been proposed.
p-block elements The block of elements in the periodic table consisting of the main groups 13 (B to Tl),
14 (C to Pb), 15 (N to Bi), 16 (O to Po),
17 (F to At) and 18 (He to Rn). The
outer electronic conÜgurations of
these elements all have the form
np
2 np
x where x = 1 to 6. Members at
the top and on the right of the pblock are nonmetals (C, N, P, O, F, S,
Cl, Br, I, At). Those on the left and at
the bottom are metals (Al, Ga, In, Tl,
Sn, Pb, Sb, Bi, Po). Between the two,
from the top left to bottom right, lie
Patterson function
400
p
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Pasteur Institute. In 1848 he discovered *optical activity, in 1860 relating it to molecular structure. In 1856
he began work on fermentation, and
by 1862 was able to disprove the existence of spontaneous generation. He
introduced pasteurization (originally
for wine) in 1863. He went on to
study disease and developed vaccines
against cholera (1880), anthrax
(1882), and rabies (1885).
Patterson function A function,
denoted P(x,y,z), used in the analysis
of the results of *X-ray crystallography. P(x,y,z) is deÜned by
P(x,y,z) = Σ
hkl
|F hkl |cos2π(hx + ky + lz),
where h, k, and l are the Miller indices of the crystal. This function is
plotted as a contour map with maxima of the contours at vector distances from the origin, i.e. vectors
from the origin to the point (x,y,z),
where the maximum occurs, corresponding to vector distances between
pairs of maxima in electron density.
Thus, the Patterson function enables
interatomic vectors, which give the
lengths and directions between
atomic centres, to be determined.
This technique, introduced by A. L.
Patterson in 1934, is called Patterson
synthesis and is most useful if the
unit cell contains heavy atoms.
Patterson synthesis See patterson function.
Pauli, Wolfgang Ernst (1900–58)
Austrian-born Swiss physicist. After
studying with Niels *Bohr and Max
*Born, he taught at Heidelberg and,
Ünally Zurich. His formulation in
1924 of the *Pauli exclusion principle explained the electronic make-up
of atoms. For this work he was
awarded the 1945 Nobel Prize for
physics. In 1931 he predicted the existence of the neutrino.
Pauli exclusion principle The
principle that no two electrons in an
atom can have all four quantum
numbers the same. It was Ürst formulated in 1925 by Wolfgang *Pauli and
more generally applies to the quantum states of all elementary particles
with half-integral spin.
Pauling, Linus Carl (1901–94) US
chemist. After spending two years in
Europe, he became a professor at the
Californian Institute of Technology.
His original work was on chemical
bonding; in the mid-1930s he turned
to the structure of proteins, for
which he was awarded the 1954
Nobel Prize for chemistry. He was
also an active campaigner against nuclear weapons and in 1962 was
awarded the Nobel Peace Prize.
Pauling’s rules A set of rules that
enables the structures of many complex ionic crystals to be understood.
These rules involve the sizes and
electrical charges of the ions and
were proposed by Linus *Pauling in
1929. They work well for mainly
ionic crystals, such as silicates, but
less well for crystals, such as sulphides, in which the bonding is
mainly covalent. Pauling put forward
his rules on the basis of empirical observations and calculations of crystal
energies. A number of extensions and
modiÜcations have been proposed.
p-block elements The block of elements in the periodic table consisting of the main groups 13 (B to Tl),
14 (C to Pb), 15 (N to Bi), 16 (O to Po),
17 (F to At) and 18 (He to Rn). The
outer electronic conÜgurations of
these elements all have the form
np
2 np
x where x = 1 to 6. Members at
the top and on the right of the pblock are nonmetals (C, N, P, O, F, S,
Cl, Br, I, At). Those on the left and at
the bottom are metals (Al, Ga, In, Tl,
Sn, Pb, Sb, Bi, Po). Between the two,
from the top left to bottom right, lie
Patterson function
400
p
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