[The idea of writing on Pauling cropped up
after writing on G.N. Ramachandran (Dream-2047, September 2001 Issue),
who was greatly influenced by Pauling. We had reproduced the poem
written by Ramachandran on Pauling. Moreover the year 2001 also
happens to be the birth centenary of Pauling].
Linus Carl Pauling is the only person to have received
two unshared Nobel Prizes - first in 1954 in chemistry for his 'research
into the nature of the chemical bond and its application to the
elucidation of the structure of complex substances', and the second
one in 1962 in Peace for his ardent pacifist campaign against nuclear
warfare. Pauling is widely regarded as one of the greatest scientists
ever. Besides being the greatest architect of chemistry, Pauling
was a founder of molecular biology and a pioneer in quantum mechanics.
Pauling combined chemistry and physics to solve various puzzles
related to the nature of chemical bond. As one of his biographers
has written Pauling's understanding of the chemical bond and molecular
architecture is probably unsurpassed in the history of chemistry.
His ideas on chemical bonding are fundamental to modern theories
of molecular structure. Pauling determined crystal structure by
X-ray crystallography and the structure of gas molecules by electron
diffraction. He ascertained the molecular cause of sickle-cell anaemia
and his observation that a molecular disorder can explain the symptoms
of an illness founded the discipline, molecular medicine. He developed
an electronegativity scale to assigning electronegativities to atoms
involved in covalent bonding. He extended the theory of covalent
bonds to include metal and intermetallic compounds. It was Pauling
who formulated the concept of resonance, a very important concept
in structural chemistry. It refers to a state where none of the
classical formulae of a chemical system is entirely consistent with
observed properties. Pauling developed unique model building techniques
that he put to use in his studies of proteins and nucleic acids.
He proposed helical structures for proteins based on polarity of
the atoms in the peptide bond. His monumental text book, The Nature
of the Chemical Bond and the Structure of Molecules and Crystals,
first published in 1939, is even today a classic in its field. The
book is one of the most important books in the history of chemistry.
It has been translated in many languages.
Pauling is much known for his controversial thesis
proposing that high doses of vitamin-C would help not only in the
prevention of common cold but also in the prevention of cancer.
In 1973, he founded the Linus Pauling Institute of Science and Medicine
in Palo Alto, California. Outside his scientific works, Pauling
took a vital interest in public affairs, especially in the movement
for world disarmament. His book No More War (1958) was a plea for
international peace. It was an instant best-seller. He strongly
opposed nuclear testing. He could gather signature and support of
11,000 scientists for his petition against nuclear testing in front
of the United Nations. Pauling was well-known for his independence,
courage, fighting qualities, brilliant wit and vigorous enthusiasm
for his work. Isaac Asimov called him 'a gentleman in highest sense
of the word." Pauling was a very controversial and outspoken
person. His uncompromising nature was reflected even in his school
Pauling was born in Portland, Oregon, USA on 28th
February 1901. His parents were Herman Henry William Pauling, a
pharmacist and Lucy Isabelle Pauling usually called Belle. His father
died when Pauling was 9 years old, forcing him to take up odd jobs
to support his mother and sisters as well as pay for his education.
We are told that by the age of nine Pauling had
read all the books available in his house. Pauling's father Herman
Pauling, in his attempt to collect proper reading material for young
Pauling, wrote to a local newspaper, the Oregonian : "I am
a father and have an only son who is aged 9 years, in the fifth
grade, a great reader and is deeply interested in ancient history…..
In my desire to encourage and assist him in his prematurely developed
inclinations I ask some of the Oregonian's interested readers to
advise me regarding the proper or atleast the most comprehensive
works to procure for him." we are told that Herman Pauling
did not receive any response.
Pauling's interest in science developed at the
very early age of 11. Pauling started collecting first insects and
then minerals. It is said that he did not stop at collecting the
objects but he proceeded to classify and catalogue them. However,
in his own words Pauling was not successful as a collector. To quote
Pauling: "I was not successful as a collector, but I got a
book from the library on mineralogy and I copied out tables of properties,
hardness and various properties, on to sheets of papers and glued
the papers to the wall in my work room."
In 1914 Pauling graduated from the Sunnyside Grammar
School and entered Portland's Washington High School. It is here
that Pauling became interested in studying chemistry. He was influenced
by one of his friends named Lloyd Jeffress, who had set up a small
laboratory in the corner of his bedroom. Pauling became fascinated
with chemistry after watching Jeffress conduct some simple experiments.
To quote Pauling : "I decided then to be a chemist and to study
chemical engineering, which was, I thought, the profession that
chemists followed:" Following his friend Jeffress, Pauling
also built a small laboratory in the basement of his house. He carried
out a lot of experiments on his own. He borrowed the chemicals needed
for his experiments from a small chemical laboratory at the abandoned
Oregon Iron and Steel Company in Oswego. This was possible because
Pauling's grandfather was a night watchman at a nearby plant. Later
recalling his early interest in chemistry Pauling would write: "I
was simply entranced by chemical phenomena, by the reaction in which
substances disappear and other substances, often with strikingly
different properties, appear."
Sickle-cell Anaemia: A Molecular
Sickel-cell anaemia is a hereditary chronic blood disorder
in which a person’s blood cells contain an abnormal
form of haemoglobin, the protein that transports oxygen
and which become incapable of carrying oxygen efficiently.
This often results in anaemia. When the blood is deprived
of oxygen the abnormal haemoglobin crystalises and distorts
the red blood cells into a sickle shaped. The presence of
sickle cells in the blood with or without accompanying anaemia,
is called sicklemia. The disease principally affects the
black population of Central Africa. Three different types
of individuals occur in such populations – those who
have two genes for normal haemoglobin and therefore do not
suffer from the disease; those with one abnormal gene and
one normal gene and are likely to suffer from anaemia and
those with two abnormal genes who suffer a chronic and eventually
fatal form of anaemia.
Pauling thought that it was an abnormality in oxygen-carrying
haemoglobin molecule found in red blood cells and not the
abnormality of the red blood cells themselves that caused
the sickle cell anaemia. Before turning to sickle cell anaemia
Pauling was working in haemoglobin. Pauling and his student
Dr. Harvey Itano demonstrated that haemoglobin found in
people having sickle cell anaemia actually differ from normal
haemoglobin molecule. Though the difference was very modest.
Only one of a total of 146 amino acids in such haemoglobin
molecule is incorrect. But such a single error was enough
to alter haemoglobin and reduce its ability to transport
Here we will discuss in little detail how Pauling
worked hard for continuing his education, with a view that it may
act as a source of inspiration to younger people. Unlike many fortunate
children, Pauling had to arrange money himself for his studies.
Before joining Oregon Agricultural College at Corvallis, Pauling
was working at a machine shop, where he was earning $100 a month
and his employer had promised to increase his salary to $250 a month
provided he decided to stay there. Pauling's mother was not in favour
of his joining the college. As stated earlier Pauling's father died
when he was nine years old. So his mother wanted Pauling to stay
at home and help her financially as she still had two young children
to raise. However, Pauling decided to join the college. Since his
mother had no means to help him, Pauling had to earn enough to meet
all his college expenses. The expenses were not very high. The college
did not charge any tuition fees and the books were inexpensive.
He lived in a cheap boarding house, where he shared a room with
a fellow student. But still he had to work hard. Describing a job
of delivering milk undertaken by him at the age of 18 he wrote:
" a very hard job, working eight hours every night from about
eight o'clock to about four o'clock with a horse pulling the milk
wagon and delivering milk to about 500 customers."
Inspite of the hard work that he had to undertake
to meet his college expenses, Pauling was able to impress his teachers
and colleagues by his studies. He had very little social life. As
his financial problem continued Pauling took up a job of paving-plant
inspector of the State of Oregon during the summer of 1919. His
job was to inspect new pavement and take samples back to the state
laboratory for analysis. His salary for the job was $125 per month.
He lived in a tent with the workmen and ate with them. He sent almost
his entire salary to his mother, expecting that his mother would
be able to help him to return to Oregon Agricultural College for
his junior year. However, the financial crisis grew worse. His mother
was suffering from pernicious anaemia. So he was compelled to decide
to continue to work as leaving-plant inspector. But then he got
an offer from Oregon Agricultural College to teach quantitative
analysis in chemistry. The offer was really extraordinary considering
the fact that Pauling was a student, who completed the course himself
six months earlier. The salary for his new assignment was $100-a-month.
His duties were to supervise laboratories and give lectures. He
had to spend 40 hours a week with students. Besides his teaching
assignment Pauling studied the works of two eminent chemists Gilbert
Newton Lewis (1875-1946) and Irving Langmuir (1881-1957). Their
works had a profound effect on Pauling. This had largely determined
the course of his work for fifty years. As he later wrote by reading
their works he developed "a strong desire to understand the
physical and chemical properties of substances in relation to the
structure of the atoms and molecules of which they are composed".
Resonance means representation of the structure
of a molecule by two or more conventional formulae. Whenever
a molecule can be represented by two or more structures having
the same arrangement of atomic nuclei but with different arrangement
of electrons – there is resonance. In such a case the
molecule is said to be a resonance hybrid of all these structures.
The molecule is somewhere in between these structures and
it cannot be represented satisfactorily by any one of them.
For example, the formula of methanal or formaldehyde can be
represented by H2 C=0, where there is a double bond in the
carbonyl group. It is known that in such compound the oxygen
atom carry some negative charge and the carbon has some positive
charge. The true bonding in the compound is somewhere between
H2C=0 and the ionic compound H2+C0- . The molecule is said
to be a resonance hybrid of the two, indicated by H2C=0 <->
H2C+0-. The two possible structures need not contribute equally
to the actual form. When the contributing structures are of
about the same stability that is with same energy content,
then resonance is important. The contribution of each structure
to the resonance hybrid is dependent on the relative stability
of that structure. If a particular structure is more stable
it will make a larger contribution than the other structure(s).
The resonance hybrid is more stable than any of the contributing
structures. This increases in stability is called the resonance
Pauling could begin his junior year in the college in the fall of
1920. On June 5, 1922 Pauling received his bachelor of science degree
from the Oregon Agricultural College. Pauling failed to get Rhodes
Scholarship inspite of being nominated by the faculty of his college
with good recommendation. In the fall of 1922 Pauling enrolled as
graduate student in the California Institute of Technology (Cal
Tech) at Pasadena. Pauling's first choice was the University of
California at Berkeley, where G.N. Lewis was the chairman of the
department of chemistry, whose works had a decisive role on Pauling's
scientific career. But Pauling did not get any response from Berkeley
in time. His second choice was the University of California at Harvard
but its scholarship offer was not matching Pauling's financial needs
The California Institute of Technology was originally
established in 1891. Before 1920 it used to be known by various
names like Throop University, Throop Polytechnique Institute and
Throop College of Technology. In its early years its academic reputation
was not very high. It became a leading research institution largely
because of the initiatives taken by George Ellery Hale (1868-1938)
, a member of the Throop Board of Trustees and then Director of
Mount Wilson Observatory. In about 1907 Hale could persuade the
other trustees to develop an outstanding institute for science and
technology on their campus. Hale was also able to persuade some
of the leading American researchers to come to Pasadena. Robert
Andrews Millikan (1868-1953), who determined an accurate value for
Planck's constant and originated the 'oil drop' experiment to measure
electronic charge, left the University of Chicago in 1918 to become
the first administrative head of the California Institute of Technology.
Millikan got Nobel Prize in 1923. Arthur Amos Noyes left the Massachusetts
Institute of Technology in 1917 to establish the Gates Chemical
Laboratory at Throop. It was Noyes who had chosen Pauling as a graduate
student. Noyes knew Pauling before his coming to Pasadena. He had
sent Pauling the proofs of his new chemistry text, Chemical Principles,
with the instruction to solve all the problems in the first nine
chapters which numbered more than 500. Pauling solved all the problems.
This helped Pauling to develop a strong background in physical chemistry.
After coming to Cal Tech, Pauling realized that he lacked on many
counts in his training at Oregon Agricultural College. To quote
him : "There were so many gaps in understanding that …often
I did not know whether to attribute this failure to myself or to
the existing state of development of science".
In March 1926 Pauling sailed for Europe, on a
two year Guggenheim Fellowship. First he went to Munich to work
with Arnold Sommerfield (1868-1951) at his Institute of Theoretical
Physics. At Munich he spent one year and wrote one of his most frequently
cited research papers: "The Theoretical Prediction of the Physical
Properties of Many-Electron Atom's and Ions". From Munich Pauling
went to Copenhagen to spend a year with Niels Bohr (1885-1962) at
the Institute of Theoretical Physics. At Copenhagen Pauling worked
with Samuel Abraham Goudsmit (1902-78) whose work on spectral analysis
eventually led to the discovery of the electron spin or fourth quantum
number. From Copenhagen Pauling went to the University of Zurich,
where he attended lectures by Erwin Schrodinger (1887-1961) and
Peter Joseph William Debye (1884-1966). After completing his two-year
European tour he came back to California Institute of Technology
to join as Assistant Professor of Theoretical Chemistry and Mathematical
Pauling worked on a variety of problems in chemistry
and biology. His early work in chemistry was on chemical bonding
and molecular structure. Though Pauling consistently referred to
himself as chemist or physical chemist, his early work involved
mathematics and physics to a great extent. His research did not
fit into any conventional definition of chemical studies. Once Pauling
wrote :"Some people seem to think that work such as mine, dealing
with the properties of atoms and molecules, should be classed with
physics but I, as I have said before, feel that the study of chemical
substances remains chemistry even though it reaches the state in
which it requires the use of considerable mathematics." Pauling
applied physical methods like X-ray diffraction, electron diffraction,
and magnetic effects to determine molecular structures.
Electronegativity denotes the easiness with
which an atom can attract electrons to itself. Electronegative
elements attract electrons, so forming negative ions. The
halogens are typical electronegative elements. Pauling devised
an electronegativity scale to indicate the relative power
of attraction of elements for electron. Fluorine, the most
non-metallic element has a value of 4.0 on this scale. Some
other values on this scale are : boron(B) 2.0, carbon(C) 2.5,
nitrogen (N) 3.0, oxygen (O) 3.5, silicon (Si) 1.8, phosphorus(P)
2.1, sulphur (S) 2.5, chlorine (Cl) 3.0, and bromine (Br)
2.8. In a covalent bond between two atoms of different electronegativities,
the bonding electrons will be located close to the more electronegative
atom, creating a dipole. Electronegativity values can be used
to show why certain substances, such as hydrochloric acid,
are acid, whereas others such as sodium hydroxide, are alkaline.
Pauling's interest in complex molecular structures
led him to work in biology and medicine. He had a strong belief
that all biological phenomena must have a molecular origin. He studied
the properties of haemoglobin using magnetic measurements. This
work led on to extensive studies of the nature and structure of
proteins. Pauling jointly with Robert B. Corey showed that the amino
acid chain in certain proteins can have helical structure. Pauling's
work provided a powerful impact to F.H.C. Crick and J.D. Watson
in their search for the structure of DNA.
Pauling made significant contributions to applying
quantum mechanics to the bonding of chemical compounds. He developed
almost all of the most fundamental principles of the modern theory
of chemical bonding including the concept of the 'hybridization
of orbital,' central to the understanding the shapes of molecules;
resonance, a state where a molecule has a structure between two
or different conventional structures and electronegativity. His
book Introduction to Quantum Mechanics published in 1935 was quite
Pauling studied the denaturation of proteins by
heat, acids, bases or chemicals such as urea. He gave a correct
interpretation of denaturation of proteins by applying the concept
of weak bonds - it is due to the loss of a set of hydrogen bonds
necessary for the stabilization of protein's three-dimensional structures.
It does not involve the breaking of a covalent bond in the molecule
or the separation of a colloidal aggregate.
Pauling explained the specificity of the antibody-antigen interaction
by the formation of certain number of weak bonds, formed between
atoms situated close together, in particular, hydrogen bonds between
the antigen and the antibody. The complementary structure of antigen
and antibody was evident from the existence of a large number of
What can we learn from Pauling's biography? Greatness
can be achieved even through tremendous hardship. In fact many a
great people had to struggle in the early years even for their bare
survival. What is important is to have determination -determination
to achieve something. But one needs to prepare for it. Self-teaching
is very important. But then it has its own limitations. Proper training
is important. Pauling could get opportunity to work with some of
the best minds of his time. So it is also important to go where
something is really happening, to get first hand experience and
to be a part of it. Teachers can play a great role in shaping the
careers of their students. This we see very often when we go through
the biographies of great scientists. Unfortunately in India today
teachers are hardly playing this role. Certainly there are exceptions.
But the general trend is that by taking the name of 'professionalism'
people are becoming more and more self-centered, often akin to being
selfish. One cannot sustain an idea in vacuum. It needs a proper
environment. In any case to achieve something one should, like Pauling,
have enormous self-confidence and an urge to live a happy, useful
and a satisfying life and help others to achieve the same. To quote
Pauling : " The evidence of my senses tells me that I am a
man like other men. When I cut myself, I am hurt, I suffer. I cry
out. I see that that when someone else cuts himself, he cries out.
I conclude from his behaviour that he is suffering in the same way
that I was…I am led to believe that I am a man like other
The Chemical Bond
The chemical bond is the force that holds
atoms together in a molecule or a mechanism by which atoms
combine to form molecules. We will say that there is a chemical
bond between two atoms or groups of atoms only when the forces
acting between them are strong enough to form an aggregate
of the atoms involved with sufficient stability to be regarded
as an independent species.
The amount of energy required to break a
bond and produce neutral atoms is known as bond energy. Atoms
combine with each other because of their tendency of acquiring
stable electronic configurations. Atoms with full outer shells,
of electrons are more stable than those with partially filled
outer shells. The noble gases or inert gases have full outer
shells and are very stable. Other atoms can acquire stable
electronic configuration by combining with other atoms to
form chemical bonds. The principal types of chemical bonds
are the ionic, covalent, metallic and hydrogen bonds. There
are other types also. The ideal cases are ionic and covalent
bonds and the remaining ones are of an intermediate type.
The Ionic Bond : results
from the attraction of oppositely charged ions. Ionic bonds
are formed by the transfer of electrons from a metallic element
to a non-metallic element. The atoms of metallic elements
lose their electrons to form positive ions while t he atom
of non-metals gain electrons to form negative ions. The resulting
highly stable ions retain their individual structures, as
they approach one another to form stable molecule or crystal.
An ionic crystal like sodium chloride is composed of independent
sodium ion (Na+) and chlorine ion(Cl-). No discrete diatomic
molecule exists and the entire crystal is a single giant molecule.
Covalent Bond : When a
non-metal combines with another non-metal, they tend to share
electrons so that the partner atoms each have a share in enough
electrons to complete their outer shells. A single covalent
bond is formed when two atoms share a pair of electrons. Unlike
in ionic bond, in the formation of covalent bond there is
no electron transfer. The attractive force is produced by
interaction of the electron pair with the nuclei of both atoms.
Double and triple bonds are formed when the atoms share more
than two electrons. Generally in covalent bonding each atom
contributes to the shared pair. Covalent bonds are of particular
importance in organic chemistry because of the ability of
the carbon atom to form four covalent bonds. But there are
cases when both electrons come from the same atom. In such
case the resulting bond has a partly ionic character and is
called a co-ordinated link.
Metallic Bond : Metallic
elements are held together by metallic bonding. The metallic
bond is responsible for crystalline structure of pure metal.
Metallic bond is not ionic because all the atoms are identical.
It is also not covalent in the ordinary sense as the valency
electrons are shared collectively by all the atoms in the
crystal. Metal atoms are packed together where each atom loses
its outer electrons into a ‘sea’ of free electrons
or mobile electrons. These free electrons are delocalised,
that is, not restricted to orbiting individual positive ions.
The mobile electrons form a kind of electrostatic ‘glue’
holding the structure together.
Hydrogen Bond : Hydrogen
bonding is a strong electrostatic attraction between two independent
molecules in which the electric charges are unevenly distributed.
Such molecules are called polar molecules and usually contain
nitrogen, oxygen and fluorine. These elements have a strong
tendency to draw electrons towards them. The hydrogen atom
acts as bridge between them. Hydrogen bond is much weaker
compared to ionic or covalent bonds. However, this plays an
important role in molecular biology.
I want to be free of suffering to the greatest
extent possible. I should like to live a happy, useful life, a satisfying
life. I want other people to help keep my suffering to a minimum.
It is my duty, accordingly, to help them, to strive to prevent suffering
for other people".
For Further Reading
1. Serafini, Antony, Linus Pauling : A Man and
His Science, New York : Paragaon House , 1989
2. White, Florence Meiman, Linus Pauling : Scientist and Crusador,
New York: Walker & Co. 1980
3. Newton, David E. Linus Pauling : Scientist and Advocate, Hyderabad
; Universities Press (India) Ltd., 1999.