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//**​ >Ancient Times**// (**[|**http://en.wikipedia.org/wiki/Democritus**]**) Date of Birth:** 460 BCE Bio:** He travelled to Asia, and was even said to have reached India and Ethiopia.We know that he wrote on Babylon and Meroe; he must also have visited Egypt, and Diodorus Siculus states that he lived there for five years. He himself declared that among his contemporaries none had made greater journeys, seen more countries, and met more scholars than himself. He particularly mentions the Egyptian mathematicians, whose knowledge he praises. Theophrastus, too, spoke of him as a man who had seen many countries. During his travels, according to Diogenes Laërtius, he became acquainted with the Chaldean magi. A certain "Ostanes", one of the magi accompanying Xerxes was also said to have taught him. After returning to his native land he occupied himself with natural philosophy. He travelled throughout Greece to acquire a knowledge of its culture. He mentions many Greek philosophers in his writings, and his wealth enabled him to purchase their writings. Leucippus, the founder of the atomism, was the greatest influence upon him. He also praises Anaxagoras. The tradition that he was friends with Hippocrates seems to have been based on spurious letters. He may have been acquainted with Socrates, but Plato does not mention him and Democritus himself is quoted as saying, "I came to Athens and no one knew me.". Though Aristotle viewed him as a pre-Socratic, it should be noticed that since Socrates was born ca. 469 BC (about 9 years before Democritus), it is very possible that Aristotle's remark was not meant to be a chronological one, but directed towards his philosophical similarity with other pre-Socratic thinkers. //**>1700-1800 >1800-1875**// ([]) Date of Birth:** 6 Sept, 1766
 * __DEMOCRITUS__
 * Date of Death:** 370 BCE
 * Country of Origin:** Greece
 * Year of Discovery:
 * Discovery:**The hypothesis of Leucippus and Democritus held everything to be composed of atoms, which are physically, but not geometrically, indivisible; that between atoms lies empty space; that atoms are indestructible; have always been, and always will be, in motion; that there are an infinite number of atoms, and kinds of atoms, which differ in shape, size, and temperature. Of the weight of atoms, Democritus said "The more any indivisible exceeds, the heavier it is." But their exact position on weight of atoms is disputed.
 * __JOHN DALTON__
 * Date of Death:** 27 July, 1844
 * Country of Origin:** England
 * Year of Discovery:** 1803
 * Bio:** John Dalton was born into a Quaker family at Eaglesfield, near Cockermouth in Cumberland, England. The son of a weaver, he joined his older brother Jonathan at age 15 in running a Quaker school in nearby Kendal. Around 1790 Dalton seems to have considered taking up law or medicine, but his projects were not met with encouragement from his relatives — Dissenters were barred from attending or teaching at English universities — and he remained at Kendal until, in the spring of 1793, he moved to Manchester. In 1794, shortly after his arrival in Manchester, Dalton was elected a member of the Manchester Literary and Philosophical Society, the "Lit & Phil", and a few weeks later he communicated his first paper on "Extraordinary facts relating to the vision of colours", in which he postulated that shortage in colour perception was caused by discolouration of the liquid medium of the eyeball.
 * Discovery:**
 * Elements are made of tiny particles called atoms.
 * All atoms of a given element are identical.
 * The atoms of a given element are different from those of any other element; the atoms of different elements can be distinguished from one another by their respective relative atomic weights.
 * Atoms of one element can combine with atoms of other elements to form chemical compounds; a given compound always has the same relative numbers of types of atoms.
 * Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process; a chemical reaction simply changes the way atoms are grouped together.

([]) __** Dalton's theory was based on the premise that the atoms of different elements could be distinguished by differences in their weights. He stated his theory in a lecture to the Royal Institution in 1803. The theory proposed a number of basic ideas:
 * __DALTON'S MODEL

All matter is composed of atoms Atoms cannot be made or destroyed All atoms of the same element are identical Different elements have different types of atoms Chemical reactions occur when atoms are rearranged Compounds are formed from atoms of the constituent elements.

Using his theory, Dalton rationalised the various laws of chemical combination which were in existence at that time. However, he made a mistake in assuming that the simplest compound of two elements must be binary, formed from atoms of each element in a 1:1 ratio, and his system of atomic weights was not very accurate - he gave oxygen an atomic weight of seven instead of eight. Despite these errors, Dalton's theory provided a logical explanation of concepts, and led the way into new fields of experimentation.

//**>1875-1900**// **__Wilhelm C. Roentgen __** 
 * Date of Birth: ** March 27, 1845 
 * Date of Death: ** February 10, 1923
 * Country of Origin: ** Germany
 * Year of Discovery: ** 1895
 * Biography: ** Born in the Lower Rhine Province of Germany. He was the only child of a merchant and manufacturer of cloth. At a young age, he moved to the Netherlands where he attended boarding school. He had ability for mechanics, a characteristic that he kept until his last days of life. In 1865 he entered the University of Utrecht to study physics but he didn’t obtain the credentials required for a normal student so he found out that he could enter the Polytechnic at Zurich by passing an examination. He passed the required examinations and began his studies as a mechanical engineering student. He was influenced greatly by Kundt and Clausius and in 1869 he graduated Ph.D. at the University of Zurich. Rontgen’s first work was published in 1870 and was about specific heats of gases, and later on by thermal conductivity of crystals. He was always an understanding person and always concerned about others. He was always shy of having an assistant, and preferred to work alone. Much of the apparatus he used was built by him with great ingenuity and experimental skill. He married Anna Bertha Ludwig in 1872 and had no children. And in 1923, he died from carcinoma of the intestine.
 * Discovery: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;"> Roentgen created an electromagnetic radiation in a wavelength modernly known as X-rays (Rontgen rays). This discovery leaded him to the first Nobel Prize in Physics in 1901. His discovery began when he noticed that if a discharge tube is enclosed in a sealed, thick black carton to prevent any light and worked the experiment in a dark room, a paper plate covered on one side with barium platinocyanide interposed in the path trace of the rays, it became fluorescent even as far as two meters from the discharge tube. Subsequently, various experiments exposed that objects of different thicknesses were placed within the path of the rays; they would demonstrate certain transparency when recorded on a photographic plate. He then experimented with his wife’s hand, following the same procedure and discovered that the photographic image revealed the shadows of the hand’s bones and of a ring she was wearing, as well as the flesh surrounding the bones. Later on, Rontgen concluded that the new rays were produced by the impact of cathode rays on a material object.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;">Website: ** <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;">[]

(**[|**http://en.wikipedia.org/wiki/Marie_Curie#New_elements**]**) Date of Birth:** 7 November 1867 In the same year Pierre Curie entered her life. He was an instructor in the School of Physics and Chemistry, the //École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris// (ESPCI). Skłodowska had begun her scientific career in Paris with an investigation of the magnetic properties of various steels; it was their mutual interest in magnetism that drew Skłodowska and Curie together. Her departure for the summer to Warsaw only enhanced their mutual feelings for each other. She was still laboring under the illusion that she would be able to return to Poland and work in her chosen field of study. When, however, she was denied a place at Kraków University merely because she was a woman, she returned to Paris. Almost a year later, in July 1895, she and Pierre Curie married, and thereafter the two physicists hardly ever left their laboratory. Their shared hobbies were only long bicycle trips and journeys abroad, which brought them even closer. Maria had found a new love, a partner and scientific collaborator that she could depend on.
 * __MARIE CURIE__
 * Date of Death:** 4 July 1934
 * Country of Origin:** Poland
 * Year of** **Discovery:** 1896
 * Bio:** Skłodowska studied during the day, and she tutored evenings, barely earning her keep. In 1893 she obtained a degree in physics and began work in an industrial laboratory at Lippman's. Meanwhile she continued studying at the Sorbonne and in 1894 earned a degree in mathematics.
 * Discovery:** Her achievements include the creation of a theory of //radioactivity// (a term coined by her), techniques for isolating radioactive isotopes, and the discovery of two new elements, polonium and radium. It was also under her personal direction that the world's first studies were conducted into the treatment of neoplasms (cancers), using radioactive isotopes.

__**<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Antoine Henri Becquerel **__ <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Date of birth: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;"> <span style="font-family: 'Verdana','sans-serif'; font-size: 8pt; mso-ansi-language: EN;">December 15, 1852 <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Date of death: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;"> <span style="font-family: 'Verdana','sans-serif'; font-size: 8pt; mso-ansi-language: EN;">August 25, 1908 <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Country of Origin: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt;"> France
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Year of Discovery: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt;"> 1896
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Biography: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt;"> He belonged to a distinguished family of scientists and scholars. His father was a professor of Applied Physics and had done research on solar radiation and on phosphorescence. Becquerel’s grandfather created the electrolytic method for the extraction of metals from their ores. In 1888 he earned his degree on Science. In 1878 he held a position as an Assistant at the Museum of Natural History, and then replacing his father on the Chair of Applied Physics at the Conservatoire des Arts et Metiers. In 1892 he became Professor of Applied Physics in the Department of Natural History at the Paris Museum, and then became a professor at the Polytechnic in 1895.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Discovery: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt;"> His findings were directed towards his father’s previous researches. He also focused on terrestrial magnetism, but was overshadowed by his discovery of natural radioactivity. Becquerel was interested in finding a link between x-rays and naturally occurring phosphorescence. He inherited from his father many supplies to work with on this experiment. He used uranium salts near a photographic plate covered with obscure paper; he realized the plate was fogged. The conclusion was that this was a property of the uranium atom. Later on, he exposed that the rays released by uranium caused gases to ionize and they varied from x-rays, as well as that they could be redirected by electric or magnetic fields.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Website: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt;"> [] <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;">


 * __Joseph John Thomson__**
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;">Date of Birth: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%; mso-ansi-language: EN;"> December 18, 1856 <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;">
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;">Date of Death: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%; mso-ansi-language: EN; mso-bidi-font-style: italic;"> August 30, 1940 <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;">
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;">Country of Origin: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;"> United Kingdom
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;">Year of Discovery: **<span style="color: black; font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;"> 1897
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;">Biography: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;"> Thomson was awarded with the Adams Prize in 1884 for his investigations about the atomic structure. After his trip to America, he accomplished the most important work of his life which consisted on a study of cathode rays culminating in the discovery of the electron in 1897. He is credited for the discovery of the electron and he made contributions to several atomic theories. Through his studies and investigations, he helped modern investigators in the creation of the television and the computer . He married Rose Elisabeth in 1890, and they had a daughter and a son, Sir George Paget Thomson (Emeritus Professor of Physics at London University), and was awarded the Nobel Prize for Physics in 1937.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;">Discovery: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;"> He created a tube that had a positively charged anode on one side and a negatively charged cathode on the other side. Afterwards he introduced a magnet on the center of the tube at equal distance from the anode and cathode, as well as discovering the negatively charged particles that were originating towards the positive magnetic field. Out of this, he concluded that negatively charged particles could be found in atoms. Another of his creations included the Plum Pudding model, which specifically suggested that protons and electrons were randomly distributed throughout an atom. The theory was erroneous but later on led to the discovery of the nucleus.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;">Website: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; line-height: 115%;"> []

([])__** The **plum pudding model** of the atom by J. J. Thomson, who discovered the electron in 1897, was proposed in 1904 before the discovery of the atomic nucleus. In this model, the atom is composed of electrons (which Thomson still called "corpuscles", though G. J. Stoney had proposed that atoms of electricity be called //electrons// in 1894) surrounded by a soup of positive charge to balance the electron's negative charge, like negatively-charged "plums" surrounded by positively-charged "pudding". The electrons (as we know them today) were thought to be positioned throughout the atom, but with many structures possible for positioning multiple electrons, particularly rotating rings of electrons (see below). Instead of a soup, the atom was also sometimes said to have had a cloud of positive charge. <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">__Robert Andrews Millikan__ **
 * __PLUM PUDDING MODEL
 * //>1900-1915//


 * Date of birth:** <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;">22nd of March, 1868 <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * Date of death:** <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;">19th of December, 1953 <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * Country of Origin:** United States of America
 * Year of Discovery:** 1910
 * Biography:** Born in Morrison, Illinois. He had a rural lifestyle during his childhood, and he attended Maquoketa High School in Iowa. For a small period of time he worked as a court reporter until he entered Oberlin College in Ohio during 1886. His favorite subjects were Greek and math, but sometime after graduating, he became interested in physics. In 1893 he obtained a master in this subject and was subsequently appointed Fellow in Physics at Columbia University. Later on, he received his Ph.D. in 1895 for his research on the polarization of light emitted by incandescent surfaces.<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;"> Millikan was an outstanding teacher, and passing through the customary grades he became a university professor in 1910, a position that he maintained until 1921. During his early years, he spent a lot of time elaborating textbooks and simplifying as much as possible the teaching of physics. Millikan made various discoveries, especially in fields like electricity, optics, and molecular physics.
 * Discovery:** His most outstanding achievement was the accurate and precise determination he made of the charge carried by an electron. He used the “falling-drop method”, and also concluded that this quantity was a constant for all electrons, in other words he demonstrated the atomic structure of electricity. He paired with Harvey Fletcher to work on an oil-drop experimentation in which they measured the charge on a single electron. The basic charge is one of the essential physical constants, and it is one of the major scientific contributions of history. The experiment consisted basically on balancing the downward gravitational force with the upward buoyant and electric forces on miniature charged droplets of oil perched by two metal electrodes. By knowing the electric field, the charge on the droplet could be specified. Through the constant repetition of the procedure, Millikan concluded that the results could be interpreted as integer multiples of a common value, perhaps the charge on a single electron.
 * Website:** []

(**[|**http://nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-bio.html**]**) Date of Birth:** 7 Oct,1885 Niels Bohr and his wife Margrethe Nørlund Bohr had six sons. Their oldest died in a tragic boating accident and another died from childhood meningitis. The others went on to lead successful lives, including Aage Niels Bohr, who became a very successful physicist and, like his father, won a Nobel Prize in physics, in 1975.
 * __NIELS BOHR__
 * Date of Death:** 18 Nov, 1962
 * Country of Origin:** Copenhagen, Denmark
 * Year of Discovery:** 1913
 * Bio:** Born to a Danish Family, he had a love for football. In 1903 Bohr enrolled as an undergraduate at Copenhagen University, initially studying philosophy and mathematics. In 1905, prompted by a gold medal competition sponsored by the Royal Danish Academy of Sciences and Letters, he conducted a series of experiments to examine the properties of surface tension, using his father's laboratory in the university, familiar to him from assisting there since childhood. His essay won the prize, and it was this success that decided Bohr to abandon philosophy and adopt physics.Bohr published his model of atomic structure in 1913.
 * Discovery:**Bohr published his model of atomic structure in 1913, introducing the theory of electrons traveling in orbits around the atom's nucleus, the chemical properties of the element being largely determined by the number of electrons in the outer orbits. Bohr also introduced the idea that an electron could drop from a higher-energy orbit to a lower one, emitting a photon of discrete energy. This became a basis for quantum theory.


 * __ Ernest Rutherford __**
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Date of birth: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;"> August 30, 1871 <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Date of death: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;"> October 19, 1937 <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Country of Origin: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt;"> <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;">New Zealand <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Year of Discovery: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt;"> 1919
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Biography: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt;"> He belonged to a family of twelve children, and his parents could barely afford his university education but he earned a scholarship. He was an outstanding student, and <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;">he subsequently graduated M.A. in 1893 with a double first in Mathematics and Physical Science. Rutherford continued with research work at for a while, and then he received the B.Sc. degree the following year. He worked with J.J Thomson at Cambridge University; they studied the effect of electricity through air as well as the spontaneous disintegration of radium. His most relevant experiment is the Alpha-rays through matter experiment, which led to the structure of the atom in 1911. He won the Nobel Prize in 1908, and his most famous quote about his experiment was: “ It was quite the most incredible event that has ever happened to me in life. It was almost as if you fired a 15 inch shell into a piece of tissue paper and it came back and hit you”. Rutherford married Mary Newton in 1900 and they had only one daughter, Eileen, who married the physicist R.H. Fowler. Rutherford's chief recreations were golf and motoring. <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Discovery: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">In 1913 with the help of H.G. Moseley, he used cathode rays to bombard atoms of various elements and demonstrated that the inner structures correspond with a group of lines which define de elements. Then each element could be assigned an atomic number and the properties of each element could be defined by the same number. In 1919, he discovered that the nuclei of some light elements could be disintegrated by the impact of energetic alpha particles coming from some radioactive source, and that during this process fast protons were emitted. He was the first to deliberately transmute one element into another.
 * <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">Website: **<span style="font-family: 'Times New Roman','serif'; font-size: 10pt;"> []


 * __PLANETARY MODEL

__**

<span style="font-family: 'Times New Roman',Times,serif; font-size: 110%; line-height: 115%;">The Planetary model, also known as the Rutherford model consisted on the model of an atom which suggested that J.J. Thomson’s Plum pudding model was inaccurate. Rutherford’s model had various fundamental modern features which included a relatively high central charge concentrated into a very diminutive volume in comparison to the rest of the atom and containing the bulkiness of the atomic mass and a number of small electrons rotating around the nucleus. <span style="font-family: 'Times New Roman',Times,serif; font-size: 11pt; line-height: 115%;">Website: [] []

([]) __**
 * __RUTHERFORD-BOHR MODEL

The Rutherford-Bohr model provided the first really useful view of the atom. It matched what scientist knew about chemical reactions and the way atoms behaved. It led to some predictions that were later proven correct. Bohr had corrected a serious flaw by recognizing that electrons had to be in orbits (energy states). But his analysis of the energy given off when an electron dropped from a higher energy orbit to a lower energy orbit didn't hold up for atoms bigger than hydrogen (the simplest atom, with only one proton and no neutrons) More work needed to be done on the model.
 * //>1915-1950//

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">__Erwin Schrodinger__ **
 * Date of birth:** <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;">August 12, 1887 <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * Date of death:** <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;">4th of January, 1961 <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * Country of Origin:** <span style="color: black; font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;">Austria-Hungary <span style="font-family: 'Times New Roman','serif'; font-size: 10pt;">
 * Year of Discovery:** 1926
 * Biography:** He was a very talented man with a broad education. Shortly, after finishing his chemistry studies, he dedicated himself to Italian painting. Then, he tried with botany which resulted in many papers about plant phylogeny. Since an early age, he liked scientific disciplines and severe logic of ancient grammar as well as German poetry. In 1906, he was a student at the University of Vienna, and during that time he was strongly influenced by Hasenohrl (Boltzmann’s successor). During these years, he became an expert of eigenvalue problems in the physics of continuous media. <span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-ansi-language: EN;">It came as a result of his dissatisfaction with the quantum condition in Bohr's orbit theory and his belief that atomic spectra should really be determined by some kind of eigenvalue problem. For this work he shared with Dirac the Nobel Prize for 1933. After some time, Schrödinger continued his research and published many papers on a variety of topics, including the problem of unifying gravitation and electromagnetism, which also absorbed Einstein and which is still unsolved. He remained greatly interested in the foundations of atomic physics. Schrödinger disliked the generally accepted dual description in terms of waves and particles, with a statistical interpretation for the waves, and tried to set up a theory in terms of waves only. This led him into controversy with other leading physicists. He married Annemarie Bertel in 1920.
 * Discovery:** His most important discovery and contribution to the atomic theory was the development of the mathematical description that portrayed the paths electrons would probably follow in their orbits around the nucleus. He created some formulas in 1926 that later on were called the basis of quantum mechanics. Schrodinger suggested that instead of Bohr’s orbits, they were in fact orbitals. The idea that electrons would follow pre-determined paths was substituted by the idea that electrons would be moving around one specific area.
 * Website:** []


 * __ THE ELECTRON CLOUD MODEL __**

<span style="font-family: 'Times New Roman',Times,serif; font-size: 110%; line-height: 115%;">Erwin Schrödinger designed a function for the Hydrogen atom that basically described a cloud-like region where the electron could probably be found. This model was based on a probable equation that could be described as the cloud model. This model portrays a background of the possible location of the electron. The red dot at the center represents an example of the electron. As the electron moves it leaves a track of where it went through, and the recollection of this traces resemble a cloud. <span style="font-family: 'Times New Roman',Times,serif; font-size: 110%;">

Website: <span style="font-family: 'Times New Roman',Times,serif; font-size: 110%;">[]

__**JAMES CHADWICK (**[|**http://nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html**]**)**__
 * Date of Birth:** 20 Oct, 1891
 * Date of Death:** July 24, 1974
 * Country of Origin:** England
 * Year of Discovery:** 1932
 * Bio:** He attended Manchester High School prior to entering Manchester University in 1908; he graduated from the Honours School of Physics in 1911 and spent the next two years under Professor (later Lord) Rutherford in the Physical Laboratory in Manchester, where he worked on various radioactivity problems, gaining his M.Sc. degree in 1913. That same year he was awarded the 1851 Exhibition Scholarship and proceeded to Berlin to work in the Physikalisch Technische Reichsanstalt at Charlottenburg under Professor H. Geiger.

During World War I, he was interned in the Zivilgefangenenlager, Ruhleben. After the war, in 1919, he returned to England to accept the Wollaston Studentship at Gonville and Caius College, Cambridge, and to resume work under Rutherford, who in the meantime had moved to the Cavendish Laboratory, Cambridge. Rutherford had succeeded that year in disintegrating atoms by bombarding nitrogen with alpha particles, with the emission of a proton. This was the first artificial nuclear transformation. In Cambridge, Chadwick joined Rutherford in accomplishing the transmutation of other light elements by bombardment with alpha particles, and in making studies of the properties and structure of atomic nuclei.

He was elected Fellow of Gonville and Caius College (1921-1935) and became Assistant Director of Research in the Cavendish Laboratory (1923). In 1927 he was elected a Fellow of the Royal Society.


 * Discovery:** In 1932, Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of //neutrons// - elementary particles devoid of any electrical charge. In contrast with the helium nuclei (alpha rays) which are charged, and therefore repelled by the considerable electrical forces present in the nuclei of heavy atoms, this new tool in atomic disintegration need not overcome any electric barrier and is capable of penetrating and splitting the nuclei of even the heaviest elements. Chadwick in this way prepared the way towards the fission of uranium 235 and towards the creation of the atomic bomb. For this epoch-making discovery he was awarded the Hughes Medal of the Royal Society in 1932, and subsequently the Nobel Prize for Physics in 1935.

([])
 * __WERNER HEISENBERG__**
 * Date of Birth:** 5 Dec, 1901
 * Date of Death:** Feb 1, 1976
 * Country of Origin:** Würzburg
 * Year of Discovery:** 1925
 * Bio:** He was the son of Dr. August Heisenberg and his wife Annie Wecklein. His father later became Professor of the Middle and Modern Greek languages in the University of Munich. It was probably due to his influence that Heisenberg remarked, when the Japanese physicist Yukawa discovered the particle now known as the meson and the term "mesotron" was proposed for it, that the Greek word "mesos" has no "tr" in it, with the result that the name "mesotron" was changed to "meson".

Heisenberg went to the Maximilian school at Munich until 1920, when he went to the University of Munich to study physics under Sommerfeld, Wien, Pringsheim, and Rosenthal. During the winter of 1922-1923 he went to Göttingen to study physics under Max Born, Franck, and Hilbert. In 1923 he took his Ph.D. at the University of Munich and then became Assistant to Max Born at the University of Göttingen, and in 1924 he gained the //venia legendi// at that University.


 * Discovery:** His new theory was based only on what can be observed, that is to say, on the radiation emitted by the atom. We cannot, he said, always assign to an electron a position in space at a given time, nor follow it in its orbit, so that we cannot assume that the planetary orbits postulated by Niels Bohr actually exist. Mechanical quantities, such as position, velocity, etc. should be represented, not by ordinary numbers, but by abstract mathematical structures called "matrices" and he formulated his new theory in terms of matrix equations.

Later Heisenberg stated his famous //principle of uncertainty//, which lays it down that the determination of the position and momentum of a mobile particle necessarily contains errors the product of which cannot be less than the quantum constant //h// and that, although these errors are negligible on the human scale, they cannot be ignored in studies of the atom.