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  • 1. Boyle, Dalton, Becquerel and Rutherford’scontribution to Atomic Theory ResearchRobert Boyle- THE FATHER OF CHEMISTRYBackground: Jan 25, 1627 Ireland Influenced by Galileo Even though he is credited as the first modern chemist he was still a metallurgist. Believed science should be rooted in experiments& experiments should consist of careful measurement. Really helped change the way people look at chemistry and science as a whole Boyle is best known for his work with gases and air.Atomic Theory Contribution develop a definition of an element helped with "the death" of the four elements He helped emphasize the importance of experiments and precise measurements. In 1655 Boyle moved to Oxford where he joined a group of natural philosophers Robert Hooke (1635-1703) entered Boyle’s employ at this time and helped him in his experiments. They built the air-pump used to create vacuums Which Boyle used to carried out many trials to elucidate the nature and importance of air. Boyle demonstrated the necessity of air for combustion, for animal breathing, and for the transmission of sound. Prior to moving from Oxford to London in 1688, he published much influential work, including New Experiments Physio-Mechanical, Touching the Spring of the Air and its Effects (1660) and The Sceptical Chymist (1661). In The Spring of The Air he described the inverse relationship between the volume of a gas and its pressure – now known as Boyle’s Law. Can’t have a table of the elements if you have not defined what elements are Age 34, Boyle published The Skeptical Chymist. overturned Aristotle’s conception of the four elements (the belief that everything was composed of earth, air, fire and water) Replaced it with the modern idea of an element—namely that an element is a substance that cannot be separated into simpler components by chemical methods. The Skeptical Chymist is recognized as the foundation-stone of modern chemistry.Pre-Boyle The history of our theory of the atom begins in Greek about 450 B.C. A philosopher namedLeucippus began thinking about whether matter could be divided in half indefinitely. He thought that atsome point matter could not be divided any more. A pupil of Leucippus, named Democritus, took his ideafurther and said that matter was made up of "atomos" or atoms which mean "unbreakable." Epicurus (341 -270 B.C.) took up the idea of atomism and wrote books on the subject. These books did not survive, but aRoman named Lucretius (96 - 55 B.C.) wrote a long poem "On the Nature of Things" which described theideas of Epicurus in great detail
  • 2. Post-Boyle Robert Boyle (1627 - 1691) was influenced by the writings of Gassendi (1592 - 1655) who hadwritten about Lucretius and atomism. Robert Boyle did experiments to prove the atomism theory. Boyleworked with gas pressures and explained the compressibility of gases on the existence of atoms. If gaseswere made of atoms that were far apart and the gas was put under pressure causing the atoms to moveclose together then the volume would decrease. Boyle’s experiments were hard to argue with becauseother scientists could repeat his experiments and make the same observations that Boyle had made.Proved atoms existed in gas>elements +4 > death of old 4 elements – experiments are importantJohn DaltonBackground: (1766–1844)Eaglesfield, England British chemist and physicist. (1801) he formulated his law of partial pressures (see Daltons law) Best remembered for Daltons atomic theory, (1803) Dalton also studied colour blindnessThrough studying meteorology study Dalton formed an interest in the gases of the air and their ultimatecomponents. This interest of gases led to Dalton’s discovery of the Atomic Theory.Dalton was a humble man with several apparent handicaps: he was poor, he was not articulate, he was not askilled experimentalist, and he was colour blind. These disadvantages are a terrible problem for a chemist,but in spite of these Dalton made his most important contribution to science called the atomic theory. Thetheory consists that matter is composed of atoms of differing weights and combine in simple ratios byweight. Dalton worked out his atomic theory during 1803-04 and developed a table of atomic weights forelements... This theory which Dalton first advanced in 1803 is the cornerstone of modern physical science.According to his theory, which he introduced in New System of Chemical Philosophy (1808-10; 1827), allatoms of the same element have the same weight, and the atomic weight of each element is different.Therefore, Dalton reasoned, atomic weight could be used to classify elements. Parts of his theory were laterproved wrong, but his ideas about atomic weight remain a key concept in chemistry and nuclear physicsAtomic Theory Contribution-Daltons atomic theory- All matter consists of tiny particles (atoms) Atoms are indestructible and unchangeable Elements are characterized by the mass of their atoms When Elements react, their atoms combine in simple, whole-number ratios Atoms can neither be created nor destroyed in chemical reaction. Atomic theory was a result of his research into gases Discovered certain gases only could be combined in certain proportions even if two different compounds shared the same common element/ group of elements. Led him to hypothesize that elements combine at the atomic stage in fixed ratios. This ratio would naturally differ in compounds due to the unique atomic weights of the elements being combined Revolutionary idea but further experimentation by himself and others confirmed his theory. At the time considered true for all reactions involving atoms-later corrected with the discovery of nuclear fission and fusion, now know that this only holds true for chemical reactions.
  • 3. Impacts Dalton’s atomic model has been perfected over time with the research and discoveries of other scientists. Now know that the atom can be divided into even smaller particles and we have even discovered the actual internal atom structure, even able to view it through modern technology. We now know that atomic weight is a product of the structure of the atoms as well. Until Dalton’s time the atom was only considered to a philosophical construct passed down by the ancient Greeks This atomic theory made possible modern chemistry and physics. This understanding the atom helped to fuel many other discoveries such as the fundamental forces and Einstein’s theory of relativity.Rutherford- Father of Nuclear PhysicsBackground 30 August 1871,New Zealand Returned to England (1907) to become Langworthy Professor of Physics in the University of Manchester Noble prize (1908),knighted in 1914, Elemented 104 In 1899, Rutherford studied the manner in which radioactive radiations penetrated sheets of aluminium. Hefound that some of the radiation could be stopped by 1/500 of a centimetre of aluminium, while the restrequired a considerably thicker sheet to be stopped. Rutherford called the first type of radiation alpha rays,from the first letter of the Greek alphabet, and the second type beta rays, from the second letter. A thirdtype of radiation, which was the most penetrating of all, was discovered in 1900 by the French physicist PaulUlrich Villard (1860 - 1934), and was called gamma rays, from the third letter of the Greek alphabet.Rutherford thought that the alpha particle, which had a mass 7000 times greater than the electron, wouldbe good for studying the structure of the atom. In what has now become the famous Gold Foil experiment,.Atomic Theory ContributionErnest Rutherfords great contribution to atomic theory was to show what happens to an element duringradioactive decay. This enabled him to construct the first nuclear model of the atom, a cornerstone ofpresent-day physics (1911) beams of particles to explore the structure of matter Used the decay of radioactive elements to produce these beams (no particle accelerator in those days) Hans Geiger and Ernest Marsden (students of ER) asked to fire Alpha Particles at some thin gold foil If the nucleus was more of a blob (as thought) they expected the particles to pass right through This happened to most hwr 1/8000 bounced back 2yrs later, after much though over these resulted, ER realised for the alpha particles to bounce back, it must hit something small dense New model of Atom- like solar system Mass concentrated at centre & elections orbits Nowadays this is incorrect and QP tells us we can’t pinpoint the exact location of the electrons Can predict they reside in shells around the nucleus
  • 4. Rutherford’s alpha scatting experiment was direct and simple Show the nature of the atomic model by the way the alpha particles bounce- he worked out where the positive charge is Rutherford came to the conclusion: most of the atom is empty space w/ very small nucleus of great mass. 1932- ER continued experimenting and firing particles at different targets James Chadwick (partners) found 2 particles in the nucleus +Protons & =neutronsAntoine Henri BecquerelBackground 15 Dec 1852, Paris French physicist awarded half the 1903 Nobel Prize in Physics Followed in father’s footsteps (solar radiation) Discovery of radioactivity Atomic Theory Contribution (Early career) research physicist, Becquerel developed laws of radiation of light from phosphorescent substances. Attending a lecture on the discovery of "X-rays," Becquerels attention captured by the mention of a fluoroscope(father invented) After, began his own study of X-rays, reproducing Wilhelm Röntgens experiments. Suspicion that fluorescent materials might emit some of these X-rays. (1896) began working with crystals of a uranium compound (potassium uranyl sulfate), which, after exposure to sunlight, emitted fluorescent light. To determine whether X-rays were being emitted by the compound, he prepared a photographic plate for use after exposing a sample of the uranium salt to the Sun. A cloudy period ensued, during which no sunlight was available. He wrapped the crystals and a copper cross in a black cloth with the photosensitive plate and put them in a drawer, intending to retrieve them later. Quite a number of rainy days followed, with no sunlight. He finally removed the plate from the drawer and developed it, expecting to see some faint evidence of emission of radiation. To his surprise, the photographic plate revealed a distinct image of the copper cross, evidence that strong radiation must have come from the uranium compound itself. Accidentally discovered the phenomenon that came to be known as "radioactivity." Describing his method to the French Academy of Sciences on January 24, 1896, he said,
  • 5. One wraps a Lumière photographic plate with a bromide emulsion in two sheets of very thick black paper, such that the plate does not become clouded upon being exposed to the sun for a day. One places on the sheet of paper, on the outside, a slab of the phosphorescent substance, and one exposes the whole to the sun for several hours. When one then develops the photographic plate, one recognizes that the silhouette of the phosphorescent substance appears in black on the negative. If one places between the phosphorescent substance and the paper a piece of money or a metal screen pierced with a cut-out design, one sees the image of these objects appear on the negative. … One must conclude from these experiments that the phosphorescent substance in question emits rays which pass through the opaque paper and reduces silver salts. Becquerel was Marie Curies doctoral adviser and collaborated with Pierre and Marie Curie in their studies of radioactivity. W/ Becquerels support, the Curies published their findings on radium in the journal of the Academy of Science in France. Marie Curie used the term "Becquerel rays" referring to the radiation discovered by Becquerel & was the first to use the term "radioactivity" to describe both Becquerel rays & the radiation that she & Pierre discovered emanating from radium. Based on his research on radiation phenomena, Becquerel declared (1899); the rays could be deflected by a magnetic field. observation suggested that at some of the radiation was composed of electrically charged particles. In 1900, he was clearly committed to the idea that the radiation had to include particles of negative charge—just like the cathode rays discovered by J.J. Thompson. In 1901, Becquerel identified uranium as the component of his experimental compound that emitted the radiation. He published ½ dozen papers exploring the phenomenon of radioactivity before turning his attention to other interests. He placed sample uranium and a photographic plate in a black bag into a drawer while waiting for clear weather to expose the uranium to sunlight for an experiment. When he developed the plate a couple days later, he found an image of the uranium rocks demonstrating the existence of radioactivity.Sourceshttps://sites.google.com/site/robertboyletheskepticalchemist/atomic-theory-contributionhttp://www.rcs.k12.va.us/chemistrynhs/advanced/01_adv_atomic/advanced_atomic.htmhttp://understandingscience.ucc.ie/pages/sci_robertboyle.htmhttp://www.universetoday.com/38169/john-daltons-atomic-model/#ixzz24B7xhUmohttp://www.rcs.k12.va.us/chemistrynhs/advanced/01_adv_atomic/advanced_atomic.htmhttp://www.nobelprize.org/nobel_prizes/chemistry/laureates/1908/rutherford-bio.htmhttp://static.newworldencyclopedia.org/1/1e/Becquerel_plate.jpglhttp://www.chemistryexplained.com/Ar-Bo/Becquerel-Antoine-Henri.html#b