Atomic theory and periodic table timeline

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Jungin MoonLisa ChataniHye-Young LeeAtomic Theory and Periodic Table Timeline350 BCAristotle1803Dalton1866Nobel1903Wright Brothers1913Mosley1665Newton1826Berzerius1895Rntgen1908Millikan1969Apollo 11400 BCDemocritus1799Proust1864Newlanda1897JJ Thomson1911Rutherford1931Bothe & Chadwick1906JJ Thomson1869Mendeleev1817Debelreiner1534CopernicusAtomic theory - 1Atomic theory - 2Periodic TableOther eventsDemocritusDemocritus, Greek philosopher, argued that everything in the universe is made up with atoms but people argued back that everything was made up with the four factors (fire, air, dirt and water)AristotleAristotles main contribution to science was his emphasis on careful observation and very detailed classification. His ideas were highly influential in Europe for about 1500 years. It was not until the Renaissance that they were questioned, most notably by Galileo. Aristotles system was not in itself rigid. But it was used by many people in the Middle Ages to justify and maintain the feudal system, a strict social order by which kings ruled over lords, who in turn ruled over peasant.Joseph Louis ProustJoseph Louis Proust published his law of definite proportions stating that when compounds are analyzed into their constituent parts they always contain the same proportions of their elements by weight. What we now know as stoichiometry led Dalton to propose his atomic theory in 1803.John DaltonJohn Dalton he published a book called A New System of Chemical Philosophy in 1808. It had two main points. One was that all chemical elements are composed of very small particles called atoms, which do not break up during chemical reactions. The other was that all chemical reactions are the result of atoms joining together or separating. Another important feature of the book was its proposal that different atoms weigh different amounts.DbereinerJohann Wolfgang Dbereiner was a German scientist. He discovered law of triads in 1817. Each of his triads was a group of three elements. The appearance and reactions of the elements in a triad were similar to each other. The relative atomic mass of the middle element in each triad was close to the average of the relative atomic masses of the other two elements. This gave other scientists a clue that relative atomic masses were important when arranging the elements.J.J. Thomson (1897 & Protons)Joseph John Thomson was a British physicist. He discovered the electron in 1897. This showed that the atom contained smaller pieces, whereas John Dalton had thought that atoms could not be broken down into anything simpler.

Joseph John Thomson demonstrated that hydrogen had only a single electron per atom. Previous theories allowed various numbers of electrons in 1906

Robert Anderson MillikanRobert Millikan was an American physicist. He did oil-drop experiments in 1909. In the experiment he measured the electric charges on tiny falling oil droplets. His study established that any particular droplet's electrical charge is a multiple of a definite, fundamental value - the electron's charge.Ernest RutherfordErnest Rutherford discovered X-Rays and uranium radiation. Rutherford and his team carried out important experiments into the structure of the atom, using particles called alpha particles, which are emitted by radioactive substances. From his experiments, Rutherford built up a detailed picture of the atom. He concluded that most atomic matter was concentrated into a tiny nucleus in the middle, which much lighter particles called electrons orbiting it, like planets around the sun. In 1908, Rutherford was awarded the Nobel Prize for Chemistry.Walter Bothe & James ChadwickIn 1930, Walther Bothe and Herbert Becker described an unusual type of gamma ray produced by bombarding the metal beryllium with alpha particles. James Chadwick recognized that the properties of this radiation were more consistent with what would be expected from Rutherford's neutral particle. Chadwick proved the existence of the neutron earned him the 1935 Nobel Prize in physics. Not only did this singular particle provide physicists with a superlative tool for investigating the atom, it was also used to produce a wide variety of new radioisotopes and permitted the initiation of nuclear chain reactions. Jns Jakob BerzeliusJns Jakob Berzelius determined the atomic weights of nearly all the elements then known. Dealing with so many elements in so many compounds motivated his creation of a simple and logical system of symbolsH, O, C, Ca, Cl, and so forthwhich is basically the same as the system we use today, except that the combining proportions of the atoms of elements in a compound were indicated as superscripts instead of our subscripts.John NewlandsJohn Newlands proposed the conception of periodicity among the chemical elements. He showed that if the elements be arranged in the order of their atomic weights, those having consecutive numbers frequently either belong to the same group or occupy similar positions in different groups, and he pointed out that each eighth element starting from a given one is in this arrangement a kind of repetition of the first, like the eighth note of an octave in music. Walter Bothe & James ChadwickIn 1930, Walther Bothe and Herbert Becker described an unusual type of gamma ray produced by bombarding the metal beryllium with alpha particles. James Chadwick recognized that the properties of this radiation were more consistent with what would be expected from Rutherford's neutral particle. Chadwick proved the existence of the neutron earned him the 1935 Nobel Prize in physics. Not only did this singular particle provide physicists with a superlative tool for investigating the atom, it was also used to produce a wide variety of new radioisotopes and permitted the initiation of nuclear chain reactions. MendeleevDmitri Mendeleev published a periodic table in 1869. He also arranged the elements known at the time in order of relative atomic mass, but he did some other things that made his table much more successful.He realised that the physical and chemical properties of elements were related to their atomic mass in a 'periodic' way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table. He predicted the properties of an undiscovered element that should fit below aluminium in his table. Henry MosleyIn 1914 Henry Mosley stated the modern periodic law. He said that when the elements are in order of increasing atomic number (number of protons they show a periodicity or repeating pattern of properties.http://hi.fi.tripod.com/timeline/timeline.htmhttp://cstl-csm.semo.edu/mcgowan/ch181/atomhist.htmhttp://scienceworld.wolfram.com/biography/Berzelius.htmlhttp://www.nobeliefs.com/atom.htmhttp://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/periodic_table/covalentbondingrev4.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/periodic_table/atomstrucrev5.shtmlhttp://www.bbc.co.uk/schools/gcsebitesize/science/edexcel_pre_2011/patterns/periodictablerev4.shtmlhttp://www.nndb.com/people/771/000091498/http://en.wikipedia.org/wiki/J._J._Thomsonhttp://www.rsc.org/chemsoc/timeline/pages/1799.htmlhttp://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/electrochemistry/berzelius.aspx

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