Atom and Its Components

Compile at least 5 profiles of individual that contribute strongly to the finding of atom and its components. Describe their backgrounds and contribution to science.

There are many scientists had gave their contributions to the finding of atom and its components. In this assignment, the 5 brilliant scientists that I would like to talk about are Neils Bohr, Joseph John Thomson, Ernest Rutherford, James Chadwick and John Dalton.

Niels Henrik David Bohr

Niels Henrik David Bohr was born on October 7, 1885, at Copenhagen, Denmark and died on November 18, 1962. His father, Christian Bohr, a devout Lutheran, was professor of physiology at the University of Copenhagen, while his mother, Ellen Adler Bohr, came from a wealthy Jewish family prominent in Danish banking and parliamentary circles.

When Bohr was young, his scientific talent was obvious. His family encouraged him to reach his full potential in this area. After his matriculation at the Gammelholm Grammar School in 1903, he entered University of Copenhagen and awarded the Gold Medal in 1905 which sponsored by the Royal Danish Academy of Sciences and Letters for his work on the measurement of surface tension using the vibrations of water jets. He also took his Master's degree in Physics in 1909 and his received his Doctor's degree in 1911 for his study of the electron theory of metals. In 1916, Bohr returned to the University of Copenhagen to assume the Chair of Theoretical Physics, which had been created for him. After a few years, Bohr devoted himself to the development of the University Institute for Theoretical Physics, which soon became an international center for research and study.

Bohr wished to find out more about the properties of matter and atoms so he moved to Manchester, England, and do research with Ernest Rutherford. Around 1912, he began work on some of his most important contributions to quantum physics. Bohr also published his own research, including a 1918 paper titled "On the Quantum Theory of Line Spectra". This paper elaborated on the correspondence principle, a concept first introduced by Bohr in 1913 that applied to the structure of spectra. Bohr's proposal that the atom existed only in a discrete set of energy states still remains relevant, known as the Bohr atomic model. Bohr's model of the atom proved essentially correct, and he won the Nobel Prize for his quantum theory studies in 1922. In 1955, Bohr organized the Atoms for Peace Conference in Geneva. He helped begin CERN, the European Council for Nuclear Research, and he received the first ever Atoms for Peace Award. His work highlighted the limitations of classical physics in dealing with the atomic level and anticipated his future explorations. He was the first to recognize the significance of encircling electrons and their relationship to the atomic nucleus.

Niels Bohr proposed the theory of the nucleus as a liquid drop. He realized the importance of the atomic number and saw that the physical and chemical properties of elements depend on the electrons in individual atoms. He stated that atoms don't radiate light while in a stable state, they only do when in between stable states after studied the series of lines in the spectrum of light produced by hydrogen. Then, he came up with “complementarity”, which is also called wave-particle duality. It states that certain waves, like light, exhibit characteristics of waves and particles.

Joseph John Thomson

Joseph John Thomson was a British physicist. He was born in Cheetham Hill, Manchester, England, on December 18, 1856 and died when he aged 83 on August 30, 1940, then was buried in Westminster Abbey. His father is a bookseller and so a publisher. He planned a career in engineering for Joseph, but since no apprenticeship could be found for him in any engineering firm, he was sent "temporarily" to college in Manchester at the age of 14. But then his father died when he was only 16. His mother came from a local textile family.

In 1870, Thomson studied engineering at University of Manchester which known as Owens College at that time. As a result of his ability and determination, he won a scholarship in 1876 and entered Trinity College, Cambridge. He engaged himself in developing mathematical models that would reveal the nature of atoms and electromagnetic process. In 1880, he obtained his BA in mathematics (Second Wrangler and 2nd Smith's prize) and MA (with Adams Prize) in 1883. After graduation, Thomson began working in the Cavendish Laboratory (1884 - 1918), as a Cavendish Professor of Physics, working on electricity and gases. At that time, he developed into a world-renowned institution. Thomson's brilliance brought him membership in the Royal Society at 27 and his appointment as Rayleigh's successor at 28. For the first quarter of the 20th century the Cavendish Laboratory, where Thomson insisted that theory should be considered "a policy, not a creed," was the world center for particle research. One of his students was Ernest Rutherford, who would later succeed him in the post. From 1918, Thomson was master of Trinity College, Cambridge, until his death on 1940.

J. J. Thomson was one of the founders of modern physics. He was awarded a Nobel Prize in 1906, "in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gases." He is known also for his discovery (1897) of the electron and his investigation of its charge and mass, his development of the mathematical theory of electricity and magnetism, and his work with "positive rays" (positive ion beams), which led to a means of separating atoms and molecules according to their atomic weights. His work with F. W. Aston gave evidence of the existence of isotopes of neon. In addition to his own research, Thomson made a significant contribution during his long tenure as director of the Cavendish Laboratory in making it a leading center for atomic research where many important developments in modern physics occurred. He was knighted in 1908 and appointed to the Order of Merit in 1912. Thomson was elected a Fellow of the Royal Society on 12 June 1884 and was subsequently President of the Royal Society from 1915 to 1920. In 1914 he gave the Romanes Lecture in Oxford on "The atomic theory".

Thomson conducts an experiment in which the rays were deflected by a magnetic field, and then deflected back again by an electric field. In the paper published in Philosophical Magazine 100 years ago in October 1997, he proved they were negatively charged particles, or corpuscles. Thomson imagined the atom as being made up of these corpuscles swarming in a sea of positive charge; this was his plum pudding model. This model was later proved incorrect when Ernest Rutherford showed that the positive charge is concentrated in the nucleus of the atom. Thomson had written numerous works include Elements of the Mathematical Theory of Electricity and Magnetism (1895, 5th ed. 1921), Conduction of Electricity through Gases (1903; 3d ed., with George Paget Thomson, 2 vol., 1928-33), and an autobiography, Recollections and Reflections (1936).

Ernest Rutherford

Ernest Rutherford, the father of nuclear physics, was a student of J.J. Thomson. He was born at Bridgewater, a small town close to Nelson, New Zealand, on August 30, 1871. Rutherford died on October 19, 1937, due to the complications of surgery. His father James Rutherford is a Scottish wheelwright, which makes and repairs wheels and wheeled vehicles while his mother, Martha Thompson Rutherford was an English schoolteacher.

Rutherford family moved to Foxhill, Nelson Province in 1877. Then Rutherford attended Foxhill School, Nelson Province from 1877 until 1883. In his early years, Rutherford did not show any special inclination towards science. By the age of ten he had read a scientific textbook, but otherwise there was not yet any sign of special interest in science and he was expecting to become a farmer when he grew up. In 1883, the family moved again to Havelock, Marlborough Sounds, which also near Nelson. At there, Rutherford attended Havelock School until 1886 and then entered Nelson Collegiate School. In 1889 he was awarded a University scholarship and further study at University of New Zealand, Wellington, where he entered Canterbury College. In 1893, he graduated M.A. with a double first in Mathematics and Physical Science and he continued with research work at the College for a short time, receiving the B.Sc. degree the following year. In 1894, he was awarded an 1851 Exhibition Science Scholarship, enabling him to go to Trinity College, Cambridge, as a research student at the Cavendish Laboratory under J.J. Thomson. In 1897, he was awarded the B.A. Research Degree and the Coutts-Trotter Studentship of Trinity College. Rutherford returned to England in 1907 to become Langworthy Professor of Physics in the University of Manchester, succeeding Sir Arthur Schuster. In 1919, he accepted an invitation to succeed Sir Joseph Thomson as Cavendish Professor of Physics at Cambridge.

In New Zealand, Rutherford conducted his first researches were concerned with the magnetic properties of iron exposed to high-frequency oscillations, and his thesis was entitled Magnetization of Iron by High-Frequency Discharges. In 1896, he designed what was then the world's most sensitive electromagnetic wave detector, capable of identifying waves at a distance of several hundred meters. His second paper, Magnetic Viscosity, was published in the Transactions of the New Zealand Institute (1896) and contains a description of a time-apparatus capable of measuring time intervals of a hundred-thousandth of a second. He also showed that x-rays cause air molecules to split into equal numbers of positively and negatively charged particles (ions). In 1899, he discovered 2 distinct radiations, which he termed alpha rays and beta rays (high speed electrons), and so noted the radioactive gas radon.

Rutherford won the Nobel Prize in Chemistry in 1908, and in the same year, working with his student Hans Geiger, he developed the Rutherford-Geiger detector, capable of detecting single particles emitted by radioactive atoms. In 1911 he described in detail the nuclear model of the atom. In 1913, working with Henry Gwyn Jeffreys Moseley, he used cathode ray bombardment to show that the inner structures of atoms can be used to assign an atomic number to each element. In 1914, he described the proton, and in 1917 he effectively created the field of nuclear physics by beginning a series of experiments showing that the nuclei of some light elements could be disintegrated by radioactivity, and that fast protons were emitted during this process. He was the first to establish the theory of the nuclear atom and to carry out a transmutation reaction in 1919, which the formation of hydrogen and oxygen isotope by bombardment of nitrogen with alpha particles. He also found out the half-life of radioactive elements and applied it to the studies of age determination of rocks by measuring the decay period of radium to lead-206.

Rutherford had published several books included Radioactivity (1904), Radioactive Transformations (1906), Radiation from Radioactive Substances, with James Chadwick and C.D. Ellis (1919, 1930), The Electrical Structure of Matter (1926), The Artificial Transmutation of the Elements (1933) and The Newer Alchemy (1937).

James Chadwick

James Chadwick was was an English Nobel laureate in physics awarded for his discovery of the neutron. He was born on October 20, 1891 at Bollington, Cheshire, England. He died on July 24, 1974 at Cambridge, England. Chadwick is the eldest son of John Joseph and Anne Mary Knowles Chadwick.

Priory, Chadwick entered Manchester High School and attending Victoria University in Manchester in 1908. He was admitted to the physics programs and was too shy to correct the error, although his intention was to study mathematics. In 1911, he graduated from the Honours School of Physics. During the next 2 years, his education was continued in Ernest Rutherford's laboratory at the same university, where he worked on the transmutation of other light elements by bombardment with alpha particles, and in making studies of the properties and structure of atomic nuclei, gaining his master's degree in 1913. In the same year, he was awarded the 1851 Exhibition Scholarship and used it proceeded his studies in the foremost German research institute, Physikalisch Technische Reichsanstalt at Charlottenburg under Professor H. Geiger at Berlin. This happened at the beginning of World War I. After Chadwick was detained as a civilian prisoner of war, he returned to England in 1919 to carry out research at Cambridge University.

In 1923, he became the assistant director of research at the Cavendish Laboratory. Rutherford thinks that there could be a particle with mass but no charge. He named it as neutron, and imagined it as a paired proton and electron, but here was no evidence for any of these ideas. So, Chadwick kept the problem in the back of his mind while working on other things. Experiments in Europe caught his eye, especially those of Frederic and Irene Joliot-Curie. They used a different method for tracking particle radiation. Chadwick repeated their experiments but with the goal of looking for a neutral particle, one with the same mass as a proton, but with zero charge. His experiments were successful. He was able to determine that the neutron did exist and that its mass was about 0.1 percent more than the proton's. He published his findings with characteristic modesty in a first paper entitled "Possible Existence of Neutron." In 1932, he awarded the 1935 Nobel Prize in Physics for his discovery of the neutron. From 1935 until 1948, Chadwick held the Lyon Jones chair of physics at the University of Liverpool. He also served as head of the British mission to the Manhattan Project and was present at the first atomic test in the New Mexico desert from 1943 until 1946. He was knighted in 1945. In 1948, he was elected master of Gonville and Caius College, a post from which he retired in 1959.

Chadwick had published many papers on the topic of radioactivity and connected problems and, with Lord Rutherford and C. D. Ellis, he is co-author of the book Radiations from Radioactive substances (1930).

John Dalton

John Dalton was born into a modest Quaker family on September 6, 1766, at Eaglesfield, Cumberland, England, and died on July 27, 1844, at Manchester, England, due to stoke, when he was aged 77. His father, Joseph Dalton, was a weaver in poor circumstances and his mother, Deborah Greenup, belonged to the Society of Friends.

Most of Dalton's life works as a teacher and public lecturer, beginning in his village school at the age of 12. He taught at a Quaker boarding school in Kendal for 10 years, and then, he moved on to a teaching position in the burgeoning city of Manchester. There he joined the Manchester Literary and Philosophical Society, which provided him with a stimulating intellectual environment and laboratory facilities.

Those concerned with the atomic theory in chemistry are the most important of all Dalton's investigations. To determine the likely atomic structure of each compound, he calculated atomic weights from percentage compositions of compounds, using an arbitrary system. The combinations of 2 elements will occur in a set sequence, if they can combine. Dalton also came to believe that the particles in different gases had different volumes and surrounds of caloric, thus explaining why a mixture of gases—as in the atmosphere—would not simply layer out but was kept in constant motion. Dalton consolidated his theories in his New System of Chemical Philosophy (1808-1827), which included various atoms and molecules. He used his own symbols to visually represent the atomic structure of compounds. Dalton proceeded to print his first published table of relative atomic weights. 6 elements appear in this table, namely hydrogen, oxygen, nitrogen, carbon, sulfur, and phosphorus, with the atom of hydrogen conventionally assumed to weigh 1. Dalton provided no indication in this first paper how he had arrived at these numbers.

There are 5 main points in Dalton's atomic theory. First, the atoms of a given element are different from those of any other element, which they can be distinguished from one another by their respective relative atomic weights. Second, all atoms of a given element are identical. Third, atoms of one element can combine with atoms of other elements to form chemical compounds, which the given compound always has the same relative numbers of types of atoms. Fourth, atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process. Fifth, elements are made of tiny particles, which called atoms. Dalton proposed an additional "rule of greatest simplicity" that created controversy, since it could not be independently confirmed.

In 1793, Dalton published Meteorological Observations and Essays. His studies led him to develop theories about water vapor and mixed gases, and in 1801 he came up with Dalton's law of partial pressures which that each component exerts the same pressure as it would if it alone made up the whole volume of the mixture in a mixture of gases. From there Dalton decided that all matter, not only gases, must consist of small particles.

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