Tuesday, May 5, 2009

Zewail, Ahmed


Egyptian-American scientist won the Nobel Prize for chemistry today for demonstrating that a rapid laser technique can observe the motion of atoms in a molecule as they occur during a chemical reaction. Ahmed Zewail was born in February 26, 1946, in Egypt where he grew up, Zewail received both his Bachelor of Science and his master's degrees from Alexandria University Alexandria. He began his professional career as an undergraduate trainee at Shell Corporation in Alexandria in 1966. After continued studies in the U.S.A. he graduated for Ph.D. in 1974 at the University of Pennsylvania. After the completion of his Ph.D., he went to the University of California, Berkeley, as an IBM research fellow. Zewail was appointed to the faculty at Caltech in 1976 at the age of 30 as an assistant professor of chemical physics. In 1982 he was tenured, as he became a full professor, and in 1990 was honored by the first Linus Pauling Chair at Caltech. At the age of 52, Zewail won the “Banjamin Franklin” prize after his latest scientific achievements known as the femto_second which is the smallest part of he second, he received the prize at a lavish ceremony attended by some 1,500 scientists, students, officials and figures, including former US Presidents Jimmy Carter and Gerald Ford. In 1999, Dr. Ahmed Zewail, a laser expert was nominated for the Nobel Prize for Chemistry and by that he is the first Egyptian to be nominated for this honourable prize. Dr. Zewail is the first originally Arab Muslim scientist to win such prize since Naguib Mahfouz, who won the literature prize in 1988, and late President Anwar Sadat, who shared the peace prize in 1978. But he is the first to take one of the prestigious awards for science. The Nobel carries an award of nearly one million dollars. Dr.Zewail currently holds both Egyptian and American Nationality. He has a family of four children and is married to Dema Zewail, a physician in public health (UCLA). His scientific family over the past 20 years consists of some 150 post-doctoral research fellows, graduate students and visiting associates. He lives in San Marino, California. Ahmed Zewail currently is the Linus Pauling Chair Professor of Chemistry and Professor of Physics at the California Institute of Technology, and Director of the NSF Laboratory for Molecular Sciences (LMS). Zewail's current research is devoted to developments of ultrafast lasers and electrons for studies of dynamics in chemistry and biology. In the field of femtochemistry, developed by the Caltech group, the focus is on the fundamental, femtosecond (10-15 second) processes in chemistry and in related fields of physics and biology.

Bohr, Aage Niels (1922- ),


Danish physicist and Nobel laureate, born in Copenhagen. The son of Niels Bohr, he assisted his father on the atomic bomb project at Los Alamos, New Mexico, during World War II. He then joined the Institute for Theoretical Physics in Copenhagen, devoting his attention to the inner structure of the atom.
In 1954 he wrote his doctoral thesis at the University of Copenhagen. It dealt with a collective motion theory of the atomic nucleus that he had developed with the United States physicist Ben R. Mottelson at the suggestion of the US physicist James Rainwater. The theory helped to explain many nuclear properties by showing that nuclear particles can vibrate and rotate so as to distort the shape of the nucleus from the expected spherical symmetry into an ellipsoid. Bohr, Mottelson, and Rainwater received the 1975 Nobel Prize for Physics for this work.
In 1963 Bohr became Director of the institute, now renamed in honour of his father. He resigned in 1970 to devote more time to research, but in 1975 he became Director of the Nordic Institute of Theoretical Atomic Physics, which shares research and facilities with the Niels Bohr Institute

Sakharov, Andrei Dmitriyavich


was the Soviet physicist most responsible for developing that nation's hydrogen bomb. He later became an internationally known social philosopher and an advocate for human right and world harmony. Harrison E. Salisbury's introduction to Sakharov's manifesto for world harmony, Progress, Coexistence, and Intellectual Freedom (1968), described Sakharov as an "Oppenheimer, Jeller, and Hans Bethe all rolled into one," who grew into a philosopher and social architect on a world scale. Graduating with honors from Moscow State University (1942), Sakharov showed intellectual talents so remarkable that he was exempted from military service to continue his studies during World War II (1939-1945). In 1945, he became an associate at the P. N. Le-bedev Physics Institute in Moscow, where he earned a Ph.D. in physical and mathematical sciences (1947). In the Soviet Union, this degree was generally reserved for more experienced scientists. Between 1948 and 1956, Sakharov was engaged in secret research on nuclear weapons specifically directing development of the hydrogen bomb. In 1953, he became the youngest scientist ever to be elected to the prestigious Soviet Academy of Sciences. In the early 1960's, while he continued his research on the theoretical aspects of controlled fusion at the Lebedev Institute, Sakharov and his wife, Yelena Bonner, became outspoken critics of human rights violations in the Soviet Union and around the world. By the mid-1960's, Sakharov's research interest had changed from nuclear physics to the nature of the universe In 1968, The New York Times printed Sakharov's Progress, Coexistence, and Intellectual Freedom. In this declaration, Sakharov laid out his plan for world peace and progress based on cooperation between the world's superpowers, with an emphasis on human rights and intellectual freedom. In 1970, Sakharov and two other physicists formed the Committee for Human Rights to give a stronger voice to their efforts to stop human rights violations within the Soviet Union. In 1975, Sakharov was awarded the Nobel Prize for Peace for his work in promoting world harmony and opposing violence
Reacting to his ceaseless criticism, the Soviet government arrested Sakharov in 1980, exiling him from Moscow to Gorki (now Nizhniy Novgorod, Russia), then an industrial center closed to foreigners. He was released in 1986 and returned to Moscow where he became part of a changed and changing government. In 1989, Sakharov was elected to the newly formed Soviet legislature, the Congress of People's Deputies. Sakharov's Memoirs, published in 1990 after his death, describe his life as a scientist and human rights advocate.

Hall, Lioyd Augustus (1894-1971)


was an African American chemist and inventor. He was granted more than 100 patents for processes used in food manufacturing and packaging, including his development of curing salts, condiments, spices, and flavors used in the meatpacking industry. Born in Elgin, Illinois, Hall received a B.S. degree in 1916 from Northwestern University. He worked briefly as a sanitary chemist at the Chicago Board of Health and as president and chemical director of Chemical Products Corporation. He then served as chief chemist and director of research at Grifrith Laboratories Inc. in Chicago from 1925 to 1946. Hall, a member of several professional societies, was the first African American to serve on the Board of Directors of the American Institute of Chemists, which presented him with its Honor Scroll Award of the Institute's Chicago Chapter in 1956. He also served on the board of the Institute of Food Technologists, which he co founded.

De Broglie, Louis Victor (1892-1987),


a French physicist, proposed the theory explaining the wave properties of electrons in 1924. His work greatly advanced the early understanding of quantum theory, the study of the parts of the atom and their behavior. In 1924, existing quantum theory stated that light waves sometimes behave like particles. Using mathematical logic, de Broglie reasoned that the particles, in turn, have wavelike properties. De Broglie's theory of "matter waves," which sent physicists everywhere thinking in new and unexpected direction, became the foundation for a new field of study-wave mechanics.
Proof of de Broglie's theory came in 1927 in experiments by physicists Clinton j. Davisson and Lester Halbert Germer, working with slow electrons, and by G. P. Thomson, working with fast electrons. For his vision, de Broglie received the 1929 Nobel Prize for physics and the Henri Poincare Medal of the Academie des Sciences. After receiving a degree in history from the Sorbonne in 1909, de Broglie took up his real interest, receiving a "license" in science from the University of Paris in 1913. During World War 1(1914-1918), he served in the radiotelegraph branch of the French Engineering Corps at the wireless station of the Eiffel Tower. Afterward, de Brogue resumed his scientific study at his brother's physics laboratory. Born into a noble French family, de Broglie was known as Prince Louis Victor Pierre Raymond de Broglie throughout his life. His ancestors served French kings in war and diplomacy from the time of Louis XIV. De Broglie's brother Maurice, also a physicist, was known for his research in nuclear physics, X rays, and radioactivity. While pursuing his lifelong interest in research, de Broglie taught theoretical physics at the Henri Poincare' Institute in Paris. In 1943, he founded the Center for Studies in Applied Mathematics at the institute to help physicists and mathematicians work together. Along with his brother, de Broglie was named to the French High Commission on Atomic Energy in 1945, and he also was a member of the Academie Francaise, which oversees French language and literature. De Broglie was elected to a number of prestigious international scientific societies and was appointed permanent secretary of the French Academy of Sciences in 1942.

Chadwick, Sir James (1891-1974),


British physicist and Nobel laureate, who is best known for his discovery in 1932 of one of the fundamental particles of matter, the neutron, a discovery that led directly to nuclear fission and the atomic bomb. He was born in Manchester and educated there at Victoria University. In 1909 he began working under the physicist Ernest Rutherford. At the end of World War I he went to the University of Cambridge with Rutherford, with whom he continued a fruitful collaboration until 1935. In that year Chadwick became professor at the University of Liverpool. From 1948 to 1958 he was Master, and from 1959 a Fellow, of Gonville and Caius College, University of Cambridge.
Chadwick was one of the first in Britain to stress the possibility of the development of an atomic bomb and was the chief scientist associated with the British atomic bomb effort. He spent much of his time from 1943 to 1945 in the United States, principally at the Los Alamos Scientific Laboratory (now the Los Alamos National Laboratory), New Mexico. A Fellow of the Royal Society, Chadwick received the 1935 Nobel Prize for Physics and was knighted in 1945.

Moseley, Henry Gwyn Jeffreys (1887-1915),


English experimental physicist who achieved the first experimental identification of the atomic number and nuclear charge of an element. Born in Weymouth, Dorset, Moseley came from a distinguished family of scientists. After studying physics at Oxford, he joined Ernest Rutherford at Manchester. His initial work was on beta emission from radium, but he soon moved on to the study of X-ray spectra, using the technique of X-ray diffraction developed by W. H. Bragg and his son, W. L. Bragg. Ever since Mendeleev's proposal of the periodic table in 1869, chemists had striven to explain the fact that the chemical properties of the elements are a periodic function of their atomic weights. By means of X-ray diffraction, Moseley established, in 1913, a relationship between the frequencies of X-ray emission lines and what he concluded must be the atom's nuclear charge, thereby confirming the suggestion of A. van der Broek that the nuclear charge indicated an element's position in the periodic table. Moseley thus provided an experimental basis for equating nuclear charge with what he called atomic number. From now on it became possible to predict, from gaps in the series of X-ray frequencies, the existence of missing elements in the periodic table. Moseley moved back to Oxford to continue his work there, but was killed two years later in the battle of Sari Bair during the Gallipoli campaign.

Bohr, Niels Henrik David (1885-1962),


Danish physicist and Nobel laureate, who made basic contributions to nuclear physics and the understanding of atomic structure.

Bohr was born in Copenhagen on October 7, 1885, the son of a physiology professor, and was educated at the University of Copenhagen, where he earned his doctorate in 1911. That same year he went to the University of Cambridge in England to study nuclear physics under J. J. Thomson, but he soon moved to the University of Manchester to work with Ernest Rutherford.

Bohr's theory of atomic structure, for which he received the Nobel Prize for Physics in 1922, was published in papers between 1913 and 1915. His work drew on Rutherford's nuclear model of the atom, in which the atom is seen as a compact nucleus surrounded by a swarm of much lighter electrons. Bohr's atomic model made use of quantum theory and the Planck constant (the ratio between quantum size and radiation frequency). The model posits that an atom emits electromagnetic radiation only when an electron in the atom jumps from one quantum level to another. This model contributed enormously to future developments of theoretical atomic physics.

In 1916 Bohr returned to the University of Copenhagen as a Professor of Physics, and in 1920 he was made Director of the university's newly formed Institute for Theoretical Physics. There Bohr developed a theory relating quantum numbers to large systems that follow classical laws, and made other major contributions to theoretical physics. His work helped lead to the concept that electrons exist in shells and that the electrons in the outermost shell determine an atom's chemical properties. He also served as a visiting professor at many universities.

In 1939, recognizing the significance of the fission experiments of the German scientists Otto Hahn and Fritz Strassmann, Bohr convinced physicists at a scientific conference in the United States of the importance of those experiments. He later demonstrated that uranium-235 is the particular isotope of uranium that undergoes nuclear fission. Bohr then returned to Denmark, where he was forced to remain after the German occupation of the country in 1940. Eventually, however, he escaped to Sweden, in peril of his life and that of his family. From Sweden the Bohrs travelled to England and eventually to the United States, where Bohr joined in the effort to develop the first atomic bomb, working at Los Alamos, New Mexico, until the first bomb's detonation in 1945. He opposed complete secrecy of the project, however, and feared the consequences of this ominous new development. He desired international control.

In 1945 Bohr returned to the University of Copenhagen, where he immediately began working to develop peaceful uses for atomic energy. He organized the first Atoms for Peace Conference in Geneva, held in 1955, and two years later he received the first Atoms for Peace Award. Bohr died in Copenhagen on November 18, 1962.

Hahn, Otto (1879-1968),


German physical chemist and Nobel laureate, whose greatest contributions were in the field of radioactivity. Hahn was born in Frankfurt-on-Main and educated at the Universities of Marburg and Munich. In 1911 he became a member of the Kaiser Wilhelm Institute for Physical Chemistry in Berlin and served as director of the institute from 1928 to 1945, when it was taken into Allied custody after World War II. In 1918 he discovered, with the Austrian physicist Lise Meitner, the element protactinium. Hahn, with his co-workers Meitner and the German chemist Fritz Strassmann, continued the research started by the Italian physicist Enrico Fermi in bombarding uranium with neutrons. Until 1939 scientists believed that elements with atomic numbers higher than 92 (known as transuranic elements) were formed when uranium was bombarded with neutrons. In 1938, however, Hahn and Strassmann, while looking for transuranic elements in a sample of uranium that had been irradiated with neutrons, found traces of the element barium. This discovery, announced in 1939, was irrefutable evidence, confirmed by calculations of the energies involved in the reaction, that the uranium had undergone fission, splitting into smaller fragments consisting of lighter elements. Hahn was awarded the 1944 Nobel Prize for Chemistry for his work in nuclear fission. It was proposed in 1970 that the newly synthesized element number 105 be named hahnium in his honour, but another naming system was adopted for transuranic elements beyond 104.

Meitner, Lise (1878-1968),


Austrian-Swedish physicist, who first identified nuclear fission. She was born in Vienna and educated at the Universities of Vienna and Berlin. In association with Otto Hahn, she helped discover the element protactinium in 1918, and was a Professor of Physics at the University of Berlin from 1926 to 1933. In 1938 she left Germany and joined the atomic research staff at the University of Stockholm. In 1939 Meitner published the first paper concerning nuclear fission. She is also known for her research on atomic theory and radioactivity. In her work she predicted the existence of the chain reaction, which contributed to the development of the atomic bomb. In 1946 she was visiting professor at Catholic University in Washington, D. C., and in 1959 she revisited the United States to lecture at Bryn Mawr College.

Soddy, Frederick (1877-1956),


British chemist and Nobel laureate. Soddy was born in Eastbourne, Sussex, and educated at Eastbourne College, the University College of Wales, and the University of Oxford. He was a lecturer in physical chemistry and radioactivity at the University of Glasgow from 1904 to 1914 and Professor of Chemistry at Oxford from 1919 to 1936, at which time he retired from academic life.

With the physicist Ernest Rutherford he began investigating radioactive transformations of atomic nuclei and eventually developed a theory of atomic structure. Soddy is particularly known for his investigations of the origin and nature of isotopes, for which he was awarded the 1921 Nobel Prize for Chemistry. His writings include such classic scientific works as Radioactivity (1904), Interpretation of the Atom (1932), The Story of Atomic Energy (1949), and Atomic Transmutation (1953), and works of a political-economic nature, including Cartesian Economics (1922), and Role of Money (1934).

Rutherford, Ernest, 1st Baron Rutherford of Nelson and Cambridge (1871-1937),


British physicist, who became a Nobel laureate for his pioneering work in nuclear physics and for his theory of the structure of the atom.

Rutherford was born on August 30, 1871, in Nelson, New Zealand, and was educated at the University of New Zealand and the University of Cambridge. He was Professor of Physics at McGill University in Montreal, Quebec, from 1898 to 1907 and at the University of Manchester in England during the following 12 years. After 1919 he was Professor of Experimental Physics and director of the Cavendish Laboratory at the University of Cambridge and also held a professorship, after 1920, at the Royal Institution of Great Britain in London.

Rutherford was one of the first and most important researchers in nuclear physics. Soon after the discovery of radioactivity in 1896 by the French physicist Antoine Henri Becquerel, Rutherford identified the three main components of radiation and named them alpha, beta, and gamma rays. He also showed that alpha particles are helium nuclei. His study of radiation led to his formulation of a theory of atomic structure, which was the first to describe the atom as a dense nucleus which electrons circle.

In 1919 Rutherford conducted an important experiment in nuclear physics when he bombarded nitrogen gas with alpha particles and obtained atoms of an isotope of oxygen and protons. This transmutation of nitrogen into oxygen was the first artificially induced nuclear reaction. It inspired the intensive research of later scientists on other nuclear transformations and on the nature and properties of radiation. Rutherford and the British physicist Frederick Soddy developed the explanation of radioactivity that scientists accept today. The rutherford, a unit of radioactivity, was named in his honour.

Rutherford was elected a fellow of the Royal Society in 1903 and served as president of that institution from 1925 to 1930. He was awarded the 1908 Nobel Prize for Chemistry, was knighted in 1914, and was made a baron in 1931. He died in London on October 19, 1937, and was buried in Westminster Abbey. His writings include Radioactivity (1904); Radiations from Radioactive Substances (1930), which he wrote with the physicists Sir James Chadwick and Charles Drummond Ellis, and which has become a standard text; and The Newer Alchemy (1937).

Haber, Fritz (1868-1934),


German chemist and Nobel laureate, best known for his development of an economical method of ammonia synthesis. Haber was born in Breslau (now Wroclaw, Poland) and educated at the Technische Hochschule in Berlin. He was appointed Professor of Physical Chemistry at the University of Berlin in 1911. Subsequently he became director of the Kaiser Wilhelm Institute for Physical Chemistry in Berlin.

During World War I Haber was chief of the German chemical warfare service, and he directed the chlorine gas attack at the second Battle of Ypres. In 1933, because of anti-Semitic policies in Germany, Haber resigned and went to Switzerland, where he died the following year.

Haber's greatest achievement was his discovery in 1913 of a process for synthesizing ammonia by the direct combination of nitrogen and hydrogen (see Nitrogen Fixation). The method was adapted to commercial use in the 1930s by the German chemist Karl Bosch. The Haber-Bosch process is used in the manufacture of explosives and in the production of fertilizers. Haber also made fundamental contributions to the field of electrochemistry. He was awarded the 1918 Nobel Prize for Chemistry.

Curie, Marie, née Maria Sklodowska (1867-1934),


French physicist and twice Nobel laureate, best known for her work on radioactivity, with her husband Pierre. Maria Sklodowska was born in Warsaw, Poland, which was then part of the Russian Empire. Her father, an ardent Polish nationalist, taught mathematics and physics at a secondary school, but was denied promotion because of his political views, which he passed on to his daughter. She won a gold medal at school and then participated in the “underground” university, which aimed at maintaining Polish culture in the face of Russian domination. There she was influenced by the high esteem in which its members held science. She found employment as a governess before joining her sister in Paris in 1891. She continued her scientific studies at the Sorbonne, where she came first in physics in 1893. In 1894 she met Pierre Curie, whom she married the following year.

Following the discovery of X-rays by Wilhelm Roentgen and the discovery of the emission of novel radiations from uranium in 1896 by Antoine Becquerel, Marie Curie turned her attention to the question of whether there were any other elements that emitted these rays. In 1898 she discovered that such rays were emitted in unexpected strength by the uranium-containing mineral pitchblende, for which she coined the term “radioactive”. Her observations led her to conclude that there was a previously unknown chemical element in the pitchblende. Both the Curies then made a Herculean effort to reduce the pitchblende chemically, repeatedly dissolving it and crystallizing it out to concentrate the unknown component. In the end they obtained a few hundredths of a gram containing the source of the radiation. From the spectrum of this material they confirmed the existence of a new element, which they named polonium after Marie Curie’s homeland. In further confirmatory experiments they found a second highly radioactive element, which they named radium. It was not until 1902 that they isolated chemically a sample of radium.

In 1903 the Curies were jointly awarded, with Becquerel, the Nobel Prize for Physics. In 1906 Pierre Curie was killed in a road accident. Thereafter Marie Curie took over Pierre’s chair, becoming the first woman to teach at the Sorbonne. She continued her theoretical work on radioactivity, introducing into physics the terms “disintegration” (the breakdown of an atom in radioactivity) and “transmutation” (the radioactive alteration of an atom into an atom of a different element). In 1911 she won the Nobel Prize for Chemistry.

During World War I Curie played an active role in the use of radiation for medical purposes, an interest that became dominant thereafter. She became perhaps the most famous woman in the world, a reputation about which she had mixed feelings, since it interfered with her scientific work, which for her always came first. However, she was able to use her fame to promote the medical uses of radium, by facilitating the foundation of radium therapy institutes in France, Poland, the United States, and elsewhere. She was thus able to give concrete expression to her belief in the value of science to humanity, a belief that she had held since her days in the Polish underground university.

Throughout the 1920s Marie Curie’s health declined and she had to have several cataract operations. Because of lack of knowledge about the dangers of radioactivity, she had been exposed during her career to massive doses of radiation. In 1934, as a consequence of this, she died of aplastic anaemia in an Alpine sanatorium.

Arrhenius, Svante August (1859-1927),


Swedish chemist, who helped lay the foundations of modern chemistry. Born near Uppsala, he was educated at the University of Uppsala and received his Ph.D. in 1884. While still a student, he studied the conductive properties of electrolytic (charge-conducting) solutions. In his doctoral thesis he formulated the theory of electrolytic dissociation. This theory holds that in electrolytic solutions, the dissolved chemical compounds in the solution are dissociated into ions, even when there is no current flowing through the solution. Arrhenius also postulated that the degree of dissociation increases as the solution becomes more dilute, a hypothesis that later turned out to be true only for weak electrolytes. His theory was initially thought to be wrong, and his thesis was given the lowest possible passing grade. Later, however, Arrhenius's theory of electrolytic dissociation became generally accepted, and eventually became one of the cornerstones of modern physical chemistry and electrochemistry.

In 1889 Arrhenius also observed that the speed of chemical reactions increases markedly when the temperature is increased, at a rate proportional to the concentration of the activated molecules. Arrhenius became Professor of Chemistry at the University of Stockholm in 1895 and Director of the Nobel Institute of Physical Chemistry in 1905. His awards and honours include the 1903 Nobel Prize for Chemistry. He wrote works on physical and biological chemistry, electrochemistry, and astronomy. In astronomy he is noted for his suggestion that life on Earth originated from living spores driven through space by the pressure of light. (See Ionization).

Curie, Pierre (1859-1906),


French physicist and Nobel laureate, best known for his work on radioactivity with his wife, Marie Curie. Pierre Curie was born in Paris and educated at home by his parents. He then studied physics at the Sorbonne. His interest turned to crystallography and in 1877, with his brother Jacques, he discovered piezoelectricity. Curie taught physics at a number of institutions before being appointed Professor at the Sorbonne in 1904. Until the mid-1890s most of Curie’s research was on magnetism and on crystals.

In 1894 he met Marie Sklodowska at the Sorbonne and married her the following year. Her subsequent research followed up the discovery of X-rays in 1895 by Wilhelm Roentgen and the discovery by Antoine Becquerel in 1896 of the emission of similarly penetrating rays from uranium. She found that these latter rays were also produced by the uranium ore pitchblende, but in quantities too great to be accounted for by the uranium alone. To help his wife to isolate the element that must be producing the bulk of these rays, Pierre Curie gave up his own research. In the course of this work they discovered and named the radioactive elements polonium and radium. For this they jointly received, with Becquerel, the Nobel Prize for Physics in 1903. They continued their joint work on radioactivity, but in 1906 Pierre Curie was killed in a road accident in Paris.

Planck, Max (1858-1947)


proposed the quantum theory in 1900 to explain how radiant energy (such as light) is given off and absorbed. The quantum theory completely revolutionized modern physics. It answered many questions and solved many problems that had puzzled scientists for years. For his work with the quantum theory, Planck won the Nobel Prize in physics in 1918. The basic concept of the quantum theory is that radiant energy, such as light, is a continuous stream of tiny packets of energy called quanta (or quantum in the singular). A quantum is the smallest amount of energy possible. Mathematically, the energy in a quantum is measured as the frequency of the radiation, V, times a universal constant, h. This constant value is also known as Planck's constant. Planck's formula applies to all forms of radiant energy, including ultraviolet light, X rays, radio waves, microwaves, and so on. An obvious conclusion that can be drawn from Planck's theory (and formula) is that forms of radiant energy with high frequencies have higher energy than those with lower frequencies. Planck proposed his theory to solve a particular experimental problem. He never expected it to become the basic principle of a new kind of physics. But this is exactly what happened. Albert Einstein and Niels Bohr quickly adopted Planck's ideas and extended them to many areas of physics. Einstein used the quantum theory to explain the photoelectric effect Bohr used the theory to explain how electrons in the outer shells of their atoms give off light energy without falling back into the nucleus. He theorized that electrons give off energy in limited bursts of quanta-not continuously.
Max Planck was born in Kiel, a city in north - western Germany, in 1858. He studied at the universities of Munich and Berlin with the great German scientists Hermann Helmholtz and Gustav Kirchhoff. Planck received a Ph.D. in physics and began teaching physics at the university level. He taught at the University of Berlin for most of his career. Planck served in many scientific associations, including the Prussian Academy of Science and the Kaiser Wilhelm Society of Berlin (later renamed the Max Planck Society). He was also made a foreign member of the Royal Society of London.
Planck enjoyed a wide range of interests outside of physics, including music, religion, and philosophy. He was also deeply concerned about justice. Planck stayed in Germany during the Nazi regime because he felt his duty to do so. But his family suffered terribly. In 1944 his son Erwin was arrested and executed for alleged participation in the plot to assassinate Hitler. Planck remained in Germany after World War II. He died in 1947.

Thomson, Sir Joseph John (1856-1940)


was the British physicist who discovered the electron, a fundamental atomic particle. Thomson received the 1906 Nobel Prize in physics for this work. In the middle 1890's, Thomson conducted a series of experiments on cathode rays. These rays are produced in a vacuum tube equipped with a positive terminal (anode) and a negative terminal (cathode). The cathode rays result when high-voltage electrical current is supplied to the cathode. Thomson believed that cathode rays were actually streams of tiny charged particles. He devised experiments to deflect, or bend, the cathode rays from their normal path in the tube. Then he worked out mathematical calculations on the experimental data. Thomson concluded that the rays were indeed composed of tiny charged particles, which he named "corpuscles." Later, the name "electron" was adopted. Thomson demonstrated that the particles are negatively charged, can generate heat, and have very little mass-about 1,000 times less mass than a hydrogen ion (proton), in fact. Furthermore Thomson showed through repeated experiments that electrons are present in many chemical elements. And he theorized (correctly) that electrons are a fundamental part of all matter
Thomson's discovery revolutionized scientific understanding of the atom. Before Thomson, most scientists had believed that the atom was indivisible, the smallest particle of matter that could exist His work proved that the atom could indeed be broken down into smaller particles. For this reason, Thomson can be considered the founder of modern atomic physics. Based on his work with electrons, Thomson proposed an atomic model. He suggested that the atom is a sphere (a round ball) with the electrons embedded throughout its inner volume. According to Thomson's model, the interior of an atom would resemble a watermelon with embedded seeds. Within the following 20 years, however, physicists Ernest Rutherford and Niels Bohr would develop a more workable atomic model.
Thomson discovered the first isotopes of a chemical element, specifically of the element neon. An isotope is a form of a chemical element that has a different atomic weight than the element in its normal form. Later, a pupil of Thomson, Francis Aston, invented the mass spectrograph. This device separates atoms of differing atomic weights in a substance. In 1903 Thomson proposed a discontinuous theory of light. By this, Thomson meant that light rays are composed of separate particles rather than continuous streams. Several years later, Einstein developed the photon theory of light This theory proposes that light is made up of packets of energy called photon£
Thomson had a great impact on the field of atomic physics as a teacher. He was director of the Cavendish Laboratory at Cambridge University for the eventful years in the 1890's and early 1900's. During this period, modern atomic physics came into being.

Ostwald, Wilhelm (1853-1932),


German physical chemist and Nobel laureate, considered one of the founders of modern physical chemistry. He was born in Riga, Latvia, and educated at the University of Dorpat (now Tartu State University). In 1881 he was appointed Professor of the Riga Polytechnic Institute and from 1887 to 1906 served as Professor of Physical Chemistry and director of the chemical laboratory at the University of Leipzig, Germany.

Ostwald is especially known for his contributions to the field of electrochemistry, including important studies of the electrical conductivity and electrolytic dissociation of organic acids. He invented a viscometer that is still used for measuring the viscosity of solutions. In 1900 he discovered a method of preparing nitric acid by oxidizing ammonia. This method, known as the Ostwald process, was used by Germany during World War I for manufacturing explosives after the Allied blockade had cut off the regular German supply of nitrates, and it is still used.

Ostwald received the 1909 Nobel Prize for Chemistry. His works include Natural Philosophy (1902; trans. 1910) and Colour Science (1923; trans. 1931). Also a famous scientist, his son, Wolfgang Ostwald, is generally regarded as the founder of colloid chemistry.

Becquerel, Antoine Henri (1852-1908),


French physicist and Nobel laureate, who discovered radioactivity in uranium. He was the son of Alexandre Becquerel, who studied light and phosphorescence and invented the phosphoroscope, and grandson of Antoine César Becquerel, one of the founders of electrochemistry.

Born in Paris, Becquerel became Professor of Physics at the Museum of Natural History in 1892 and at the école Polytechnique in 1895. In 1896 he accidentally discovered the phenomenon of radioactivity in the course of his research on fluorescence. After placing uranium salts on a photographic plate in a dark area, Becquerel found that the plate had become blackened. This proved that uranium must give off its own energy, which later became known as radioactivity.

Becquerel also conducted important research on phosphorescence, spectroscopy, and the absorption of light. In 1903 Becquerel shared the Nobel Prize for Physics with the French physicists Pierre Curie and Marie Curie for their work on radioactivity, a term Marie Curie coined. His works include Recherches sur la phosphorescence (Research on Phosphorescence, 1882-1897) and Découverte des radiations invisibles émises par l'uranium (Discovery of the Invisible Radiation Emitted by Uranium, 1896-1897).

Gibbs, Josiah Josiah (1839-1903)


was perhaps the greatest U.S. scientist before 1900. Although not understood or appreciated by his contemporaries, Gibbs made important contributions to the science of thermodynamics. Thermodynamics deals with forms of energy and conversion of energy from one form to another. The principles of thermodynamics can be applied to many uses. One use is the study of efficiency in machines. Another application of thermodynamics is the calculation of energy loss or gain in chemical reactions.
Gibbs applied the principles of thermodynamics to physical chemistry. His work in this field has earned him the nickname, "the father of modern physical chemistry." One of Gibbs' most important contributions was his formulation of the phase rule. This is a logical description of the physical relationships among the different states of a substance, such as water, ice, and water vapor. Gibbs' most famous written work is On the Equilibrium ofHeterogeneous Substances, published between 1875 and 1878 in the Transactions of the Connecticut Academy One of the great scientists of the age, physicist James Clerk Maxwell in England, recognized Josiah Gibbs' genius. But few Americans thought highly of him. Josiah Gibbs was born into an academic New England family. His father was a professor at Yale University in New Haven, Connecticut Josiah himself attended Yale University and in 1863 won the first doctorate of engineering awarded in the United States. After ex tended travels in Europe in the late 1860's, Gibbs returned to a professorship at Yale. There he spent the remaining years of his professional life.

Mendeleyev, Dmitry Ivanovich (1834-1907),


Russian chemist, best known for his development of the periodic table of the properties of the chemical elements. This table displays a periodicity (regular pattern) in the elements' properties when they are arranged according to atomic weight.

Mendeleyev was born in Tobolsk, Siberia. He studied chemistry at the University of St Petersburg, and in 1859 he was sent to study at the University of Heidelberg. There he met the Italian chemist Stanislao Cannizzaro, whose views on atomic weight (see Atom) influenced his thinking. Mendeleyev returned to St Petersburg and became Professor of Chemistry at the Technical Institute in 1863. He became Professor of General Chemistry at the University of St Petersburg in 1866. Mendeleyev was a renowned teacher, and, because no good textbook in chemistry was available, he wrote the two-volume Principles of Chemistry (1868-1870), which became a classic.

During the writing of this book, Mendeleyev tried to classify the elements according to their chemical properties. In 1869 he published his first version of what became known as the periodic table. In 1871 he published an improved version of the periodic table, in which he left gaps for elements that were not yet known. His chart and theories gained increased acceptance when three predicted elements—gallium, germanium, and scandium—were subsequently discovered.

Mendeleyev's investigations also included the study of the chemical theory of solution, the thermal expansion of liquids, and the nature of petroleum. In 1887 he undertook a solo balloon flight to study a solar eclipse.

In 1890 he resigned from the university as a consequence of his progressive political views and his advocacy of social reforms. In 1893 he became director of the Bureau of Weights and Measures in St Petersburg and held this position until his death.

Monday, May 4, 2009

Maxwell, James Clerk (1831-1879)


was one of the greatest physicists in history. Like another great British physicist, Sir Isaac Newton, he investigated many different areas of physical science. Also like Newton, he contributed theories that opened new avenues of thought and scientific development
Maxwell's work on electricity, magnetism, and force fields was his greatest achievement. In this area of research, he built on theories that Michael Faraday had developed. Maxwell and Faraday exchanged ideas on this subject (Faraday died in 1867.) Faraday studied the electromagnetic force field produced by electrical current He became convinced that the forces at work in such a field are not confined to the conductor The conductor is, rather, simply a medium through which the force is exerted. The logical conclusion of this idea is that lines of force extend into the space that surrounds a conductor. Faraday's idea was an original and important one. But he was not able to work it out completely.
Maxwell took Faraday's idea and developed it into a complete electromagnetic theory This theory explains how electrical current radiates energy-such as radio waves and microwaves-into space. Eventually the electromagnetic theory was applied to the physical properties of radioactive materials and the energy they produce and to other types of energy as well. Maxwell then applied principles of electromagnetic theory to light. He discovered that light behaves in the same way as electromagnetic forces and concluded that light is a type of electromagnetic force.Several years later, in the 1880's, the German physicist Heinrich Hertz produced radio waves in a laboratory selling. Hertz's experiments completely confirmed Maxwell's electromagnetic theory The importance of Maxwell's electromagnetic theory can hardly be overestimated. For the most part, twentieth century technology would have been impossible without it. Inventions such as television, radio, radar, satellite communications, and many others are a result of electromagnetic theory. In fact, communications as we know them would be unthinkable without Maxwell's pioneering work And without the long-distance communications made possible by electromagnetic waves, there would be no space exploration.
Furthermore, Maxwell's work laid the theoretical foundations for an avalanche of scientific developments to come. Development of the quantum theory-probably the most important scientific theory of our century-is partly an outgrowth of Maxwell's study of light and other electromagnetic energy. His development of field theory-the study of force fields created by magnetism, electricity, or other natural forces-also strongly influenced later physicists. Albert Einstein, for example, spent much of his later life trying to formulate a unified field theory that would explain all forces in the universe in unified, mathematical terms. This work, which continues today, would have been impossible without Maxwell's basic theories. Maxwell made important contributions to other areas of science. He developed a kinetic theory of gases that helped clarify the nature of gases. In this theory, Maxwell explained the behavior of a gas in terms of the movement of its molecules. He calculated mathematically the movements of the molecules and showed how these individual movements, multiplied billions of times, explained many properties of gases. This work enabled chemists to determine mathematically-and to predict-the characteristics of a gas.
Maxwell developed a theory of color vision and made one of the first color photographs. He also studied the rings of the planet Saturn. Maxwell studied the work of contemporary and previous scientists and learned from them. He was particularly interested in the work of Henry Cavendish, a great English scientist of the 1700's who had been largely ignored in his own time. Maxwell drew on Cavendish's work with electricity in formulating his own theories. Maxwell also tried to draw public attention to the scientific achievements of Cavendish, who had died in 1810. He published in 1879 some of the scientific papers by Cavendish on electricity.
In the early 1870's, descendants of Henry Cavendish endowed a scientific laboratory at Cambridge University. James Clerk Maxwell accepted the invitation to become the first Cavendish professor of physics. He designed the laboratory and recruited its staff. Maxwell's published scientific writings include Theory of Heat and Treatise on Electricity and Magnetism.

Kekule Von Stradonitz, Friedrich August (1829-1896)


was a German chemist who laid the foundations of modern organic chemistry. Organic chemistry is the field of research and industry that is concerned with chemical compounds based on carbon. Because of its particular atomic structure, carbon is able to form a tremendous number and variety of compounds. Carbon atoms can link with other carbon atoms as well as with atoms of other elements. Carbon often bonds with hydrogen, oxygen, nitrogen, or various combinations of these elements. All life as we know it is based on organic chemistry. Also, all the fossil fuels that we use are organic compounds. So are many medicines, including penicillin, for instance. Today, chemical research laboratories constantly synthesize, that is, make, new organic compounds. These are used for many purposes, from plastics to insect-killing substances. Kekule' discovered several important principles of organic chemistry. First, he realized that the carbon atom is tetravalent; that is, it has four valences. A valence is the ability of one electron of an atom to combine with free electrons of other atoms. Thus, carbon has four such free electrons. Kekule' also understood that the four valences in a carbon atom are spread evenly apart. As a result, the structure of the carbon atom can be imagined as a tetrahedron (a pyramid with equal sides). This idea is helpful when examining the structure of organic compounds.
From these insights, Kekule' concluded that carbon and other elements bond together to form long chains of molecules. Kekule' then applied his new understanding to the study of benzene, an organic substance. Kekule' tried tc determine the chemical structure of benzene. He grappled with this problem with little success. Then one night in a dream, he saw the benzene molecule as a snake chasing its tail in a circle. When he woke up, Kekule' knew he had the solution for benzene's molecular structure: it is shaped like a ring. This story that often been quoted as a striking example of the subconscious (dreaming) mind helping the conscious (waking) mind solve a problem. Kekule's solution of benzene structure opened new avenues of study and research in organic chemistry.

Wohler, Friedrich (1800-1882),


German educator and chemist, born in Eschersheim (now part of Frankfurt-on-Main), and educated at the Universities of Marburg and Heidelberg. While studying medicine at Heidelberg, he became interested in chemistry and went to Stockholm to study with the Swedish chemist Baron Jons Jakob Berzelius. In 1836 he became Professor of Chemistry at the University of Gِttingen.

A pioneer in the field of organic chemistry, Wohler is famous for his synthesis of the organic compound urea. By this contribution he proved, contrary to scientific thinking of the time, that a product of the living processes of animals could be made in the laboratory from inorganic materials. Wohler also conducted important research on uric acid and the oil of bitter almonds, in collaboration with the German chemist Baron Justus von Liebig, and isolated the chemical elements aluminium and beryllium. He discovered calcium carbide and prepared acetylene from it; he also developed the method for preparing phosphorus that is in common use today. He wrote a number of textbooks on organic and inorganic chemistry.

Faraday,Michael (1791-1867),


an English chemist and physicist, made very important contributions to scientific knowledge of electricity and magnetism. His work helped make possible the development of electrical power. Moreover, Faraday's theories on electricity and magnetism established the basis for more complete theoretical understanding of these forces.
Faraday also made important discoveries in chemistry. Only a handful of scientists in the 1800's made as great an impact on later developments in science and technology as Faraday. As a young man, Faraday served as assistant to Sir Humphry Davy, the great chemist. Eventually, Faraday made important chemical discoveries on his own. He isolated benzene, an organic compound, and described its molecular structure. He was the first to synthesize compounds out of the elements carbon and chlorine. In the 1820's, however, Faraday turned his affention to electricity and magnetism. These topics became the scientific passion of his life. Faraday is most remembered for his work wit~ them. Jwo physicists had made important discoveries about electricity in the early 1820's. Physicist Hans Christian Oersted, a Dane, discovered that electrical current flowing through a wire produces a magnetic field around the wire. Then, French physicist Andre-Mane Ampere found that the magnetic field produced in this way is circular. As a result, the field around a current-carrying wire has the shape of a cylinder. A cylinder is a type of circular shape in space, like a can or a tube.
Faraday extended this understanding of electricity and magnetism. He speculated that a magnetic pole would move constantly in a circular path through the electromagnetic field around a current-carrying wire. Faraday proved this idea experimentally. He developed a device in which a magnet is left free at one end to rotate around a wire when current is applied. Faraday's experiment worked as he had suspected-and also demonstrated for the first time the principle of the electric motor. Faraday's next important discovery--of electrical induction-came in 1831. When a current is started in a wire, the process is called electromagnetic induction. Faraday found that the current could be started, or induced, by moving a magnet in and out of a coil of wire. This discovery several months earlier. But Faraday published his results first. Faraday had a strong interest in the theoretical aspects of science. He was dissatisfied with making such discoveries as electromagnetic induction without also understanding thE underlying physics. To this end he devoted much of his scientific career. Although he never completely worked out electromagnetic theory, his ideas deeply influenced later physicists. Many scientists of Faraday's time thought that electricity is a liquidlike substance that flows through wires just as water flows through pipes. Faraday, however, gradually developed radically different ideas. He believed that electricity was caused by build-up of tension or strain in maffer. The tension increases to a breaking point; then it is passed outward from the source. The build-up and release of tension occurs in rapid cycles, and tension is distributed in waves. Later scientific understanding would show Faraday's concept of electrical current to be remarkably accurate
In later life, Faraday further refined these ideas. He theorized on the way force fields-such as those created by electricity, magnetism, or gravity-work in space that is not occupied by maffer. These ideas laid the groundwork for later development of field theory, which considers the nature of force fields. James Clerk Maxwell, a British physicist active in the later 1800's, developed these ideas mathematically. Faraday's experimental work in electricity also led to important discoveries in electrochemistry. He discovered the mathematical relationship between electricity and the valence, that is, the combining power, of a chemical element. Faraday's law states this relationship. It gave the first clue to the existence of electrons
Michael Faraday was born in 1791 in a country village in Surrey, England. He came from a rather poor family. The Faradays belonged to a small Protestant religious group called the Sandemanians. The strict, simple piety of Faradav's childhood deeply affected his thinking throughout life. Though little opportunity was available to the child of a rural, poor blacksmith at that time, young Michael managed to get a job with a bookbinder. This proved a fortunate turn of fate, because the work enabled Faraday to get books to read. During this time, Faraday came upon a book about electricity. Thus began his lifelong interest in electricity. Unable to afford higher education, the teen-ager set up his own crude laboratory and conducted experiments. The second great stroke of fortune in Faradays youth was to become acquainted with the chemist Sir Humphry Davy. A combination of Faradays own persistent efforts and good luck led to his appointment as Davy's assistant in 1813. Faraday was a lilile over 20 years old at the time. This marked the beginning of a long, productive scientific career for the young man. In addition to his experimental work, Faraday became one of the most popular lecturers of his day. Tragically, during the last decade or so of his life, Faraday sank into senility, a condition in which one's mental powers decline. Queen Victoria provided a house for the great scientist to live out his days. Faraday died in 1867. The farad, a unit used to measure electrical capacitance, was named for him.

Berzelius, Jons Jakob, Baron (1779-1848), Swedish chemist, considered one of the founders of modern chemistry.


Berzelius was born near Linkoping. While studying medicine at the University of Uppsala, he became interested in chemistry. After practising medicine and lecturing, he became a professor of botany and pharmacy at Stockholm in 1807. From 1815 to 1832 he was Professor of Chemistry at the Caroline Medico-Chirurgical Institute in Stockholm. He became a member of the Stockholm Academy of Sciences in 1808, and in 1818 became its permanent secretary. For his contributions to science, Berzelius was made a baron in 1835 by Charles XIV John, King of Sweden and Norway.

Berzelius's research extended into every branch of chemistry and was extraordinary for its scope and accuracy. He discovered three chemical elements—cerium, selenium, and thorium—and was the first to isolate silicon, zirconium, and titanium. He introduced the term catalyst into chemistry and was the first to elaborate on the nature and importance of catalysis. He introduced the present system of chemical notation, in which each element is represented by one or two letters of the alphabet. In addition, Berzelius was primarily responsible for the theory of radicals, which states that a group of atoms, such as the sulphate group, can act as a single unit through a series of chemical reactions. He developed an elaborate electrochemical theory that correctly states that chemical compounds are made up of negatively and positively charged components. All of his theoretical work was supported by elaborate experimental measurement. His greatest achievement was the measurement of atomic weights