New chemistry

New chemistry

Antoine Lavoisier revolutionized chemistry. He named the elements carbon, hydrogen and oxygen; discovered oxygen’s role in combustion and respiration; established that water is a compound of hydrogen and oxygen; discovered that sulfur is an element, and helped continue the transformation of chemistry from a qualitative science into a quantitative one.

Lavoisier announced a new fundamental law of nature; the law of conservation of mass:

matter is conserved in chemical reactions

In 1789 Lavoisier published his groundbreaking Elementary Treatise on Chemistry. It contained a list of chemical elements. The list included oxygen, nitrogen, hydrogen, sulfur, phosphorus, carbon, antimony, cobalt, copper, gold, iron, manganese, molybdenum, nickel, platinum, silver, tin, tungsten, and zinc.

Dalton's fascination with gases gradually led him to formally assert that every form of matter (whether solid, liquid or gas) was also made up of small individual particles called Atoms.

The main points of Dalton's atomic theory, as it eventually developed, are:

• Elements are made of extremely small particles called atoms.
• Atoms of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass and other properties.
• Atoms cannot be subdivided, created or destroyed.
• Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
• In chemical reactions, atoms are combined, separated or rearranged.

In an article he wrote for the Manchester Literary and Philosophical Society in 1803, Dalton created the first chart of atomic weights.

In 1808,In A New System of Chemical Philosophy, Dalton introduced his belief that atoms of different elements could be universally distinguished based on their varying atomic weights. In so doing, he became the first scientist to explain the behavior of atoms in terms of the measurement of weight. He also uncovered the fact that atoms couldn't be created or destroyed.

Following the Karlsruhe meeting in 1860, values of about 1 for hydrogen, 12 for carbon, 16 for oxygen, and so forth were adopted. This was based on a recognition that certain elements, such as hydrogen, nitrogen, and oxygen, were composed of diatomic molecules and not individual atoms.

An important long-term result of the Karlsruhe Congress was the adoption of the now-familiar atomic weights (actually, atomic masses) of approximately 1 for hydrogen, 12 for carbon, 16 for oxygen, Cl 35.5, K39, Ca 40, Br 80, Rb 85, Sr 88, I 127, Cs 133, Ba 137 and so forth.

On March 6, 1869, Mendeleev made a formal presentation to the Russian Chemical Society, entitled The Dependence between the Properties of the Atomic Weights of the Elements, which described elements according to both weight and valence. This presentation stated that:

1. The atomic mass, exhibit an apparent periodicity of properties.
2. Elements which are similar as regards to their chemical properties have atomic weights which are either of nearly the same value (e.g., Pt, Ir, Os) or which increase regularly (e.g., K, Rb, Cs).
3. The arrangement of the elements in groups of elements in the order of their atomic weights corresponds to their so-called valencies, as well as, to some extent, to their distinctive chemical properties; as is apparent among other series in that of Li, Be, B, C, N, O, and F.
4. The elements which are the most widely diffused have small atomic weights.
5. The magnitude of the atomic weight determines the character of the element, just as the magnitude of the molecule determines the character of a compound body.
6. We must expect the discovery of many yet unknown elements–for example, two elements, analogous to aluminium and silicon, whose atomic weights would be between 65 and 75.
7. The atomic weight of an element may sometimes be amended by a knowledge of those of its contiguous elements. Thus the atomic weight of iodine (126.9).
8. Certain characteristic properties of elements can be foretold from their atomic weights.

In 1900 Electron was discovered as a subatomic particle.

Electron was discovered by J. J. Thomson in Cathode Ray Tube (CRT) experiment.

1. Electrons are negatively charged particles with charge-to-mass ratio −1.76×10⁸ C/gm
2. The charge of an electron was measured by R. Millikan in Oil drop experiment.
3. Charge of an electron is −1.60×10⁻¹⁹ C
4. Mass of an electron is 9.1×10⁻²⁸ gram.
5. Electron is approximately 2000 times lighter than hydrogen.

Rutherford proposed the following structural features of an atom:

1.Most of the atom’s mass and its entire positive charge are confined in a small core, called nucleus. The positively charged particle is called proton.

2.Most of the volume of an atom is empty space.
3.The number of negatively charged electrons dispersed outside the nucleus is same as number of positively charge in the nucleus. It explains the overall electrical neutrality of an atom.

But scientists soon realized that the atomic model offered by Rutherford is not complete. Various experiments showed that mass of the nucleus is approximately twice than the number of proton. What is the origin of this additional mass?

In 1930, W. Bothe and H. Becker found an electrically neutral radiation when they bombarded beryllium with alpha particle. They thought it was photons with high energy (gamma rays).

• In 1932, Irène and Frédéric Joliot-Curie showed that this ray can eject protons when it hits paraffin or H-containing compounds.
• The question arose that how mass less photon could eject protons which are 1836 times heavier than electrons. So the ejected rays in bombardment of beryllium with alpha particles cannot be photon.
• In 1932, James Chadwick performed the same experiment as Irène and Frédéric Joliot-Curie but he used many different target of bombardment besides paraffin. By analyzing the energies of different targets after bombardment he discovered the existence of a new particle which is charge-less and has similar mass to proton. This particle is called neutron. Beryllium undergoes the following reaction when it is bombarded with alpha particle: Be⁹ + ᾳ⁴ → C¹² + C¹³ + ꞑ

Einstein's Postulates

Einstein’s Postulates

 So where was the ether wind?

The null result of the Michelson-Morley experiment baffled the physics community. Why was the ether wind undetectable? A number of attempts were made to explain this unexpected finding.

It was finally left to a young patent clerk, in 1905, to make the bold suggestion that the Michelson-Morley experiment was actually a vital clue to the very nature of time and space itself. The visionary difference here was the realization that there was no ether at all!

In 1905, while working as a patent clerk, the 26-year-old Albert Einstein published three scientific papers in one issue of the Annalen der Physik. This issue of the physics journal has since become a unique collector’s item because any one of those three papers, alone, would have won Einstein the Nobel Prize in physics.

Ironically, of the three papers, Einstein was awarded the Nobel Prize in 1921 for his paper on the photoelectric effect, and not for the one on the theory of relativity, the theory synonymous with his name. Relativity—Einstein’s main work—was apparently still being disputed in 1921. This was hardly surprising given the bizarre nature of relativity. Effects like time dilation, length contraction, and distortions in space-time, were not exactly your everyday intuitive events. How then did Einstein reason his way to such apparently fantastical scientific conclusions?

In his 1905 paper “On the Electrodynamics of Moving Bodies”, Einstein introduces the two postulates that form the starting point for his theory of relativity. The first of these postulates, which Einstein calls the “Principle of Relativity” gives his whole theory its name.

The Principle of Relativity abolishes the idea of an absolute state of rest. All observers moving at constant velocity relative to each other thus have equal status; no observer can claim to be the “special one” at rest. For example, a man standing on a train station may claim that he is stationary while his friend on the train is moving. His friend, however, may claim, instead, that he is the one actually at rest while the man on the platform is moving. Both are equally correct. According to Einstein, all velocities are relative. Hence, an object’s designated velocity conveys little meaning unless we also know which frame of reference we are viewing this velocity from.

While this first postulate may be revolutionary, it is nonetheless reasonably intuitive, i.e. it feels logical in a “common sense” way.

 Einstein’s next postulate, however, is extremely counter-intuitive, and weird consequences arise from it. Unlike the first postulate, this one defies common sense. The second postulate states that the speed of light is constant relative to all frames of reference.

Why this is so weird? If we observe a flash of light while standing on Earth, we will find it travelling from us at 300,000 km per second. Another observer, travelling in the same direction as this light ray, should then measure its speed, relative to himself, to be slower. He is, after all, chasing after it. Einstein’s second postulate, however, states that this simply does not happen.

Let us look at an analogous situation. If we are in a police car chasing after a getaway car, we would expect the getaway car to move away from us at a slower speed (relative to us). If the police car manages to move at the same speed as the getaway car, the getaway car would not even be moving away from us at all. Its velocity relative to us would then be zero, since we are keeping up with it. This would be common sense.

Now imagine the scenario if the getaway car behaves like Einstein’s light ray. What happens then is this. The getaway car continues to pull away from the police car at the same speed, no matter how fast the police car chases after it. It’s the ideal getaway car. It runs away from us at exactly the same speed no matter how we race after it.

The really strange thing is this. A man standing on the pavement also sees this same getaway car pulling away from him at the same speed as we do in the police car. In other words, the speed of the getaway car relative to the man on the pavement, and relative to us in the police car chasing after it, is exactly the same! For example, if the getaway car is pulling away from the man on the pavement at 100 km per hour, it is also pulling away from us in the police car at 100 km per hour, even though we are tearing after it as fast as we can. How can this be? Surely this defies common sense.

This weird behaviour of the getaway car is, nonetheless, what Einstein is proposing for the light ray. The same light ray travels away from all observers at the same speed of 300,000 km per second, regardless of whether the observer is stationary or moving. The velocity of the observer makes no difference whatsoever. The speed of light is constant relative to all frames of reference. This then is Einstein’s second postulate. It sounds positively crazy!

Nonetheless, this second postulate of relativity has passed the test of time. It has survived a whole century of close scientific scrutiny, and has become a fundamental cornerstone of all modern physics. How do we explain this phenomenon?

Actually, Einstein never gave an explanation for his second postulate. That, in fact, is why it is called a postulate. A postulate is a principle simply assumed to be true, and then used as the basis for further derivations and conclusions. For some reason, Einstein’s second postulate works. But why does it work? And why is nature so strange? That was the question Heisenberg, on his deathbed, was purportedly still puzzling over. Why—Heisenberg was essentially asking—does relativity exist at all ?

Albert Einstein

Albert Einstein

 The German-born physicist Albert Einstein developed the first of his groundbreaking theories while working as a clerk in the Swiss patent office in Bern. After making his name with four scientific articles published in 1905, he went on to win worldwide fame for his general theory of relativity and a Nobel Prize in 1921 for his explanation of the phenomenon known as the photoelectric effect. An outspoken pacifist who was publicly identified with the Zionist movement, Einstein emigrated from Germany to the United States when the Nazis took power before World War II. He lived and worked in Princeton, New Jersey, for the remainder of his life.

 Einstein’s Early Life (1879-1904)

Born on March 14, 1879, in the southern German city of Ulm, Albert Einstein grew up in a middle-class Jewish family in Munich. As a child, Einstein became fascinated by music (he played the violin), mathematics and science. He dropped out of school in 1894 and moved to Switzerland, where he resumed his schooling and later gained admission to the Swiss Federal Polytechnic Institute in Zurich. In 1896, he renounced his German citizenship, and remained officially stateless before becoming a Swiss citizen in 1901.

While at Zurich Polytechnic, Einstein fell in love with his fellow student Mileva Maric, but his parents opposed the match and he lacked the money to marry. The couple had an illegitimate daughter, Lieserl, born in early 1902, of whom little is known. After finding a position as a clerk at the Swiss patent office in Bern, Einstein married Maric in 1903; they would have two more children, Hans Albert (born 1904) and Eduard (born 1910).

Einstein’s Miracle Year (1905)

While working at the patent office, Einstein did some of the most creative work of his life, producing no fewer than four groundbreaking articles in 1905 alone. In the first paper, he applied the quantum theory (developed by German physicist Max Planck) to light in order to explain the phenomenon known as the photoelectric effect, by which a material will emit electrically charged particles when hit by light. The second article contained Einstein’s experimental proof of the existence of atoms, which he got by analyzing the phenomenon of Brownian motion, in which tiny particles were suspended in water.In the third and most famous article, titled “On the Electrodynamics of Moving Bodies,” Einstein confronted the apparent contradiction between two principal theories of physics: Isaac Newton’s concepts of absolute space and time and James Clerk Maxwell’s idea that the speed of light was a constant. To do this, Einstein introduced his special theory of relativity, which held that the laws of physics are the same even for objects moving in different inertial frames (i.e. at constant speeds relative to each other), and that the speed of light is a constant in all inertial frames. A fourth paper concerned the fundamental relationship between mass and energy, concepts viewed previously as completely separate. Einstein’s famous equation E = mc2 (where “c” was the constant speed of light) expressed this relationship.

From Zurich to Berlin (1906-1932)

Einstein continued working at the patent office until 1909, when he finally found a full-time academic post at the University of Zurich. In 1913, he arrived at the University of Berlin, where he was made director of the Kaiser Wilhelm Institute for Physics. The move coincided with the beginning of Einstein’s romantic relationship with a cousin of his, Elsa Lowenthal, whom he would eventually marry after divorcing Mileva. In 1915, Einstein published the general theory of relativity, which he considered his masterwork. This theory found that gravity, as well as motion, can affect time and space. According to Einstein’s equivalence principle–which held that gravity’s pull in one direction is equivalent to an acceleration of speed in the opposite direction–if light is bent by acceleration, it must also be bent by gravity. In 1919, two expeditions sent to perform experiments during a solar eclipse found that light rays from distant stars were deflected or bent by the gravity of the sun in just the way Einstein had predicted.

The general theory of relativity was the first major theory of gravity since Newton’s, more than 250 years before, and the results made a tremendous splash worldwide, with the London Times proclaiming a “Revolution in Science” and a “New Theory of the Universe.” Einstein began touring the world, speaking in front of crowds of thousands in the United States, Britain, France and Japan. In 1921, he won the Nobel Prize for his work on the photoelectric effect, as his work on relativity remained controversial at the time. Einstein soon began building on his theories to form a new science of cosmology, which held that the universe was dynamic instead of static, and was capable of expanding and contracting.

 Einstein Moves to the United States (1933-39)

A longtime pacifist and a Jew, Einstein became the target of hostility in Weimar Germany, where many citizens were suffering plummeting economic fortunes in the aftermath of defeat in the Great War. In December 1932, a month before Adolf Hitler became chancellor of Germany, Einstein made the decision to emigrate to the United States, where he took a position at the newly founded Institute for Advanced Study in Princeton, New Jersey. He would never again enter the country of his birth.

My school and education

My School and Education

               We were fetching well-water outside our home, when Vithal, my uncle asked me to come to school, with him to Ranjol. He also guided me to take the money needed for admission [Rs 0.5]. I put forth the idea with my grandma, Narasamma and she readily gave the coin from her pocket. I was happy to see the new world, the school. The monsoon rains filled the air with delighting breath; I accompanied my uncle to NTMS Ranjol-Kheni.

It was the only school available for a population of ten villages. The modern school was constructed in the outs-curt of the village Kheni Ranjol. I was admitted to the first standard and asked to sit with students in the last room, on the floor. There was a wooden chair placed for the class teacher. The teacher entered the room with the attendance register and sat on the chair. Immediately, a leg of the chair cracked to the weight of young healthy teacher Mr. Gurubasappa. We all started laughing, and he too laughed.

The office room was centrally located on the premises and was large enough to accumulate many people. The headmaster Basavanappa Sativar, was sitting there with other teachers. It was a new world to a village boy like me who had never gone out of my street.

After a few months, a new teacher was appointed to my own village Hochakanalli and I was asked to attend to this school. The school was running from a private building since there was no public room constructed yet. We were about a dozen boys attending this school. I started learning alphabets of the Kannada language and Kannada numerals. By the first few months, I was able to read the first standard book. Then the teacher offers me 2^nd standard book and by the summer-end, I completed this book also. I was declared passed, the second standard.

For the next year, I again went to Ranjol and was admitted to the third standard. I stood first in the class in my studies. This trend I continued till my 7th board exam and passed with first-class marks in 1966. I had scored 90% marks in mathematics paper. I had the least marks in my science subject. Both my parents were illiterates.

I was awarded a merit scholarship of Rs 50/ while in the 8^th class. But I lost my dear father while I was in 9^th class. It was a suicide. This changed the equation of our family, as we lost the bread-earning member. Mother was suffering from ill-health. Mother forced me to get married after my sslc exam in1969. I scored 67% marks in sslc. I was dreaming of going to college for a degree. I sold 10g gold which was offered in my marriage and got admission to BVB College Bidar. I became a roommate of my brother-in-law, Shri Gundappa who was a BA final year student.

On my poor financial condition, I was given free ship after my PUC Science examination, and the money which I gave as a tuition fee was refunded to me. This same money I used for next year's admission to B.Sc. part-one course. By the by I had applied for a National loan scholarship and was selected for this and completed my science degree in 1973 with second-class merit. I was appointed as a telephone operator in the month of  July1974 and I was posted to work from Bhalki telephone exchange. I worked there for five years and wrote a departmental competitive examination for promotion to the Phone Inspector post. I was selected and trained for six months at RTTC Hyderabad in 1980.

Then I again wrote the competitive exam for the post of Junior Engineer and was selected and was posted to Raichur Telephones, after 14 months of training at RTTC Trivandrum. After serving for a period of 15 years, I was promoted as Sub-Divisional Engineer and worked at Bidar for one decade, and opted for retirement in 2009 at the age of 58 years. By this time, my children have well educated and started earning for their life independently.

Satyendra Nath Bose

Satyendra Nath Bose

Indian physicist Satyendra Nath Bose discovered what became known as bosons and went on to work with Albert Einstein to define one of two basic classes of subatomic particles. Much of the credit for discovering the boson, or "God particle," was given to British physicist Peter Higgs, much to the chagrin of the Indian government and people.

Early Life and Education

Physicist Satyendra Nath Bose was born in Calcutta (now Kolkata), West Bengal, India, on January 1, 1894, the eldest and only male of seven children. Bose was a brainiac early on. He passed the entrance exam to the Hindu School, one of India's oldest schools, with flying colors and stood fifth in the order of merit. From there, Bose attended Presidency College, where he took an intermediate science course and studied with renowned scientists Jagadish Chandra Bose and Prafulla Chandra Ray.

Bose received a Bachelor of Science in mixed mathematics in 1913 from Presidency College and a Master of Science in the same subject in 1915 from Calcutta University. He received such high scores on the exams for each degree that not only was he in first standing but, for the latter, he even created a new record in the annals of the University of Calcutta, which has yet to be surpassed. Fellow student Meghnad Saha, who would later work with Bose, came in second standing.

Between his two degrees, Bose married Usha Devi at age 20. After completing his master's degree, Bose became a research scholar at the University of Calcutta in 1916, and began his studies on the theory of relativity. He also set up new departments and laboratories there to teach undergraduate and graduate courses.

Research and Teaching Career

While studying at the University of Calcutta, Bose also served as a lecturer in the physics department. In 1919, he and Meghnad Saha prepared the first English-language book based on German and French translations of Albert Einstein's original special and general relativity papers. The pair continued to present papers on theoretical physics and pure mathematics for several years following.

In 1921, S N Bose joined the physics department at the University of Dhaka, which had then been recently formed, and went on to establish new departments, laboratories and libraries in which he could teach advanced courses. He wrote a paper in 1924 in which he derived Planck's quantum radiation law without referencing classical physics—which he was able to do by counting states with identical properties. The paper would later prove seminal in creating the field of quantum statistics. Bose sent the paper to Einstein in Germany, and the scientist recognized its importance, translated it into German and submitted it on Bose's behalf to the prestigious scientific journal Zeitschrift für Physik. The publication led to recognition, and Bose was granted a leave of absence to work in Europe for two years at X-ray and crystallography laboratories, where he worked alongside Einstein and Marie Curie, among others.

Einstein had adopted Bose's idea and extended it to atoms, which led to the prediction of the existence of phenomena that became known as the Bose-Einstein Condensate, a dense collection of bosons—particles with integer spin that were named for Bose.

The Indian government honored Bose in 1954 with the title Padma Vibhushan, the second-highest civilian award in India. Five years later, he was appointed as the National Professor, the highest honor in the country for a scholar. Bose remained in that position for 15 years. Bose also became an adviser to the Council of Scientific and Industrial Research, as well as president of the Indian Physical Society and the National Institute of Science. He was elected general president of the Indian Science Congress and president of the Indian Statistical Institute. In 1958, he became a Fellow of the Royal Society.

G N Lewis

G N Lewis

Gilbert N. Lewis, in full Gilbert Newton Lewis, (born Oct. 23, 1875, Weymouth, Mass., U.S.—died March 23, 1946, Berkeley, Calif.), American physical chemist best known for his contributions to chemical thermodynamics, the electron-pair model of the covalent bond, the electronic theory of acids and bases, the separation and study of deuterium and its compounds, and his work on phosphorescence and the triplet state (in which the quantum number for total spin angular momentum is 1)

Lewis spent his youth in Lincoln, Neb. Initially educated at home by his parents, at age 13 he entered the preparatory school of the University of Nebraska in Lincoln. He continued at the university through his sophomore year before transferring to Harvard University in 1893, from which he received a bachelor’s degree in chemistry in 1896. After a year of teaching at Phillips Academy in Andover, Mass., he returned to Harvard to complete a master’s degree in 1898, followed by a doctorate the next year under the supervision of Theodore Richards for a dissertation on the electrochemistry of zinc and cadmium amalgams.

After graduation, Lewis remained at Harvard as an instructor for a year. He then pursued postgraduate work in the laboratories of Wilhelm Ostwald and Walther Nernst in Germany, before he returned for another three years as an instructor at Harvard and then a year in the Philippine Islands as superintendent of weights and measures. In 1905 Lewis joined the faculty of the Massachusetts Institute of Technology in Cambridge, and in 1912 he was appointed permanent dean of the college of chemistry and chair of the department of chemistry at the University of California at Berkeley, where he remained until his death at age 70 of an apparent heart attack while working in his laboratory. During his 34-year tenure at Berkeley, Lewis succeeded in molding its chemistry department into one of the best in the United States.

Chemical Thermodynamics:

Lewis’s major area of research was the field of chemical thermodynamics. In 1899 there was still a large gap between thermodynamic theory and practice. There was a complete theory of chemical equilibria, developed 20 years earlier by the American physicist Josiah Willard Gibbs, which showed that chemical equilibrium was determined by the free energies of the reacting substances. On the other hand, there was a vast amount of unorganized data on the enthalpies of reaction of chemical substances, collected earlier in the century by such chemists as Julius Thomsen of Denmark and Pierre-Eugène-Marcellin Berthelot of France. In addition, a series of empirical laws, dealing with the behaviour of ideal gases and dilute solutions, were developed that formed the substance of the newer physical chemistry championed by such chemists as Ostwald, Svante Arrhenius in Sweden, Jacobus van ’t Hoff in the Netherlands, and Nernst. Lewis set himself the task of closing this gap between theory and practice. This required that he either directly measure the missing free-energy values for chemical substances or supplement the existing enthalpy data with entropy values, which would allow their calculation. Second, it was also necessary to find some way of extending the empirical laws to include the behaviour of real gases and concentrated solutions.

In pursuit of the first of these goals, Lewis initiated a vigorous experimental program designed to measure the missing free-energy and entropy values. In pursuit of the second goal, he successively introduced the concepts of fugacity (1901), activity coefficient (1907), and ionic strength (1921; a measure of the average electrostatic interactions among ions in a solution). These efforts culminated in 1923 in the publication of Thermodynamics and the Free Energy of Chemical Substances, written in collaboration with chemist Merle Randall.

Chemical Bonding Theory

A second important thread in Lewis’s research centred on his speculations on the role of the newly discovered electron in chemical bonding. Though his first attempts in this area date as early as 1902, he did not publish on the subject until 1913—and then only to comment critically on attempts of others to formulate similar theories. In 1916 Lewis finally published his own model, which equated the classical chemical bond with the sharing of a pair of electrons between the two bonded atoms. Most students know of Lewis today because of “electron dot diagrams,” which he introduced in this paper to symbolize the electronic structures of atoms and molecules. Now known as Lewis structures, they are discussed in virtually every introductory chemistry book.

Shortly after publication of his 1916 paper, Lewis became involved with military research. He did not return to the subject of chemical bonding until 1923, when he masterfully summarized his model in a short monograph entitled “Valence and the Structure of Atoms and Molecules.” His renewal of interest in this subject was largely stimulated by the activities of the American chemist Irving Langmuir, who between 1919 and 1921 popularized and elaborated Lewis’s model. Many current terms relating to the chemical bond, such as covalent and the octet rule, were actually introduced by Langmuir rather than Lewis.

The 1920s saw a rapid adoption and application of Lewis’s model of the electron-pair bond in the fields of organic and coordination chemistry. In organic chemistry, this was primarily due to the efforts of the British chemists Arthur Lapworth, Robert Robinson, Thomas Lowry, and Christopher Ingold; while in coordination chemistry, Lewis’s bonding model was promoted through the efforts of the American chemist Maurice Huggins and the British chemist Nevil Sidgwick. Though Lewis occasionally published on his bonding model throughout the 1920s, he stopped writing on the subject after 1933 and left the task of reconciling the model with the newer quantum mechanics of Austrian physicist Erwin Schrödinger and German physicist Werner Heisenberg in the hands of the American chemist Linus Pauling. Pauling transformed it into the valence bond model and made it the subject of his classic book, The Nature of the Chemical Bond (1939).

Deuterium, Acid-Base Theory, And The Triplet State

Between 1933 and 1934, Lewis published more than 26 papers dealing with the separation and study of the properties of deuterium and its compounds. This was followed by a brief period of interest in neutron refraction (1936–37) and by his classic work on the electronic theory of acids and bases (1938). Now universally known as the Lewis acid-base definitions, these concepts define an acid as an electron-pair acceptor and a base as an electron-pair donor. First proposed, almost as a passing thought, in his 1923 monograph on chemical bonding, discussions of Lewis acids and bases are now found in most introductory chemistry textbooks. Almost simultaneously with his work on acid-base theory, Lewis also began his classic research on the triplet state and its role in determining the nature of the fluorescence, phosphorescence, and colours of organic dyes, which continued until his death.