jackgomesandwalterbulter

The Development of the Atom

__**Democritus**__- 460 BC-370 BC

Worked in a time period in which no modern technology was avaible.
 * [[image:democritus_7.jpg width="187" height="189" align="left" caption="Democritus"]]Born:** 460 BC
 * Country of Origin:** Greece

Was a greek philosopher who theorized that matter was ultimately composed of small, indivisible particles he called atomos, or "atoms".

__**Aristotle**__- 384 BC-322 BC


 * [[image:aristotle.jpg width="206" height="162" align="left" caption="Aristotle"]]Born**: 384 BC in
 * Country Of Origin**: StagiraGreece

Aristotle drew a significant distinction between things of two sorts: //__those that move only when moved by something else, and those that are capable of moving themselves__//. In separate documents, Aristotle not only proposed a proper description of things of each sort but also attempted to explain why they function as they do.

He came up with the original four causes for operation of matter in the world, They were:
 * **material cause-** //Is the matter of which something is made up of.//
 * **formal cause-** //This is the pattern of which the substance is formed by.//
 * **efficient cause-** //Is the binding agent in bringing togethor the matter to form this substance.//
 * **final cause-** //Is the purpose of why substance exists.//


 * __Kanada__**- 6th Century

> > > > John Dalton- 1766-1844 > **Born**: September 6,1766
 * Born**: 6th Century BCE
 * Country of Origin**: India [[image:jacky.jpg width="202" height="257" align="right"]]
 * Founded the Vaisheshika school of philosophical thought.
 * The idea was that matter was made of a finite number of paramāṇus, which is a fancy word for atoms, indivisible and eternal. Each type of atom has its own unique individuality. Atoms make up the 4 catergories:water, fire, earth and air, which make up all other matter. They had various theories about how these atoms combine, and believed the interactions are ultimately caused by the will of Ishvara, a Hindu god. [[image:canada.gif width="301" height="148" align="center"]]
 * **Country Of Origin**: England
 * He is called the father of modern atomic theory for his work about the topic and when he proposed his [[image:ii_atom.gif width="227" height="200" align="right"]]atomoic theory way back in 1805 there where 4 basic principles:
 * 1) chemical elements are made of atoms.
 * 2) the atoms of an element are identical in their masses
 * 3) atoms of different elements have different masses
 * 4) atoms only combine in small, whole number ratios such as 1:1, 1:2, 2:3 and so on.
 * 5) atoms can be neither created nor destroyed
 * 4) atoms only combine in small, whole number ratios such as 1:1, 1:2, 2:3 and so on.
 * 5) atoms can be neither created nor destroyed

Antoine Lavoisier- 1743-1794

Born: August 26, 1743 Country of Origin: France

>  He is most noted for his discovery of the role oxygen plays in combustion. French scientist during the eighteenth century, is commonly referred to as a Father figure, such as John Dalton, except his field was that of Chemistry**.** He achieved such a distinguished title by his ingenious discoveries in the areas of respiration and combustion. He revealed the true nature of science by transforming the accepted theoretical structure at the time. > > > In 1777 Lavoisier presented his theory that combustion and related processes were reactions in which oxygen combines with other elements in a paper entitled Memoir on Combustion in General

William Crookes- 1832-1919

Born: June 17,1832 > Country of Origin: England > > In 1861, while conducting a examination of residue left in the making of sulphuric acid, he observed a bright green line which had not been noticed previously, and by following up the indication he succeeded in isolating a new element, **thallium**, a specimen of which was shown in public for the first time at the exhibition of 1862. During the next eight years he carried out investigations of this metal and its properties. While determining its atomic weight, he thought it desirable, for the sake of accuracy, to weigh it in a vacuum, and even in these circumstances he found that the balance behaved in an anomalous manner, the metal appearing to be heavier when cold than when hot. > > Following these expirements he was led to his famous researches on the phenomena produced by the discharge of electricity through highly exhausted tubes, CROOKS TUBE, and to the development of his theory of "radiant matter".

Wilhelm C. Rontgen- 1845-1940

> Born: March 27,1845 > Country of Origin: Germany He has made many discovery's in his life but he is chiefly associated with the discovery of the rays that he called X-rays. In 1895 he was studying the phenomena accompanying the passage of an electric current through a gas of extremely low pressure or a vaccum. and found that, if the discharge tube is enclosed in a sealed, thick black carton to exclude all light, and if he worked in a dark room, a paper plate covered on one side with barium platinocyanide placed in the path of the rays became fluorescent even when it was as far as two metres from the discharge tube. During subsequent experiments he found that objects of different thicknesses interposed in the path of the rays showed variable transparency to them when recorded on a photographic plate. When he immobilised for some moments the hand of his wife in the path of the rays over a photographic plate, he observed after development of the plate an image of his wife's hand which showed the shadows thrown by the bones of her hand and that of a ring she was wearing, surrounded by the penumbra of the flesh, which was more permeable to the rays and therefore threw a fainter shadow. This was the first "röntgenogram" or "X-ray"ever taken.

Joseph John " JJ" Thompson-1856-1940

Born: December 18, 1856 Country of Origin: England

He discovered a method for separating different kinds of atoms and molecules by the use of positive rays, an idea developed by Aston, Dempster and others towards the discovery of many isotopes.

He discovered a even smaller and more fundamental particle called the electron and discovered that electrons are negatively charged, and are much lighter than atoms.

In his "plum pudding" model the negatively charged electrons where held in a sphere of postiviely charged electrons.

Henri Becquerel- 1852-1908

Born: December 15, 1852 Country of Origin: Paris, France

He had inherited from his father a supply of uranium salts, which phosphoresce on exposure to light. When the salts were placed near to a photographic plate covered with opaque paper, the plate was discovered to be fogged. The phenomenon was found to be common to all the uranium salts studied and was concluded to be a property of the uranium atom. Later, Becquerel showed that the rays emitted by uranium, which for a long time were named after their discoverer, caused gases to ionize and that they differed from X-rays in that they could be deflected by electric or magnetic fields. For his discovery of spontaneous radioactivity Becquerel was awarded half of the Nobel Prize for Physics in 1903.

Marie Curie- 1867-1934

Born: November 7, 1867 Country of Origin: Poland

Her early researches, together with her husband, were often performed under difficult conditions, laboratory arrangements were poor and both had to undertake much teaching to earn a livelihood. The discovery of radioactivity by Henri Becquerel in 1896 inspired the Curies in their brilliant researches and analyses which led to the isolation of polonium, named after the country of Marie's birth, and radium. Mme. Curie developed methods for the separation of radium from radioactive residues in sufficient quantities to allow for its characterization and the careful study of its properties, therapeutic properties in particular

Together with her husband, she was awarded half of the Nobel Prize for Physics in 1903, for their study into the spontaneous radiation discovered by Becquerel, who was awarded the other half of the Prize. In 1911 she received a second Nobel Prize for Chemistry in recognition of her work in radioactivity.

Ernest Rutherford-1871-1937

Born: ugust 30, 1871 Country of Origin: New Zealand

Rutherford who had worked under JJ Thompson and helped with his "plum pudding" model, performed an expirement in an attempt to varify it. His experiment proved it to be false instead. In his eperiment,Rutherford shot positively charged particicles- known as alpha particiles- at a ultra thin sheet of gold foil. These particiles were to act as the structure of the gold atoms. Rutherford performed the expirement, but the results were not as he expected. A majority of the particiles did pass directly through the foil, but sometimes particicles were deflected, and even some bounced back.

Rutherford was honored for this expirment and many others with a Nobel Prize in 1908.

Robert Millikan-1868-1953

Born:March 22, 1868 Country of Origin: USA

Millikan wrote textbooks and after he stopped writing textbooks and set out on one last try at a new line of research: the determination of the elementary unit of electric charge.

The Millikan oil-drop experiment was far superior to previous determinations of the charge of an electron. Where other workers had attempted to measure the quantity by observing the effect of an electric field on a cloud of water droplets, Millikan used single drops, first of water and then, when he found these evaporating, of oil. His measurement was off by only 0.5%, and most of this error was due to his adoption of a plausible but wrong value for the viscosity of air. The experiment had broader significance than a simple refinement of a number. Millikan emphasized that the very nature of his data refuted conclusively the minority of scientists who still held that electrons (and perhaps atoms too) were not necessarily fundamental, discrete particles. And he provided a value for the electronic charge which, when inserted in Niels Bohr's theoretical formula for the hydrogen spectrum, accurately gave the Rydberg constant—the first and most convincing proof of Bohr's quantum theory of the atom.

>

Neils Bohr- 1885-1962 > Birth Place: in Copenhagen, Denmark > > Accomplished many things for the development and structure of an atom in his life. A highly educated man he received his doctorate in physics from the University of Copenhagen in 1911. Apon graduation he traveled to england to study with another highly talented scientist, Earnest Rutherford. He would later expand on Rutherford's theroy on the structure of an atom stating that instead of the theroy of having an atom with a positively charged nucleus and negatively charged electrons in orbit around it. Bohr said that the electrons travel only in certain successively larger orbits. He suggested that the outer orbits could hold more electrons than the inner ones, and that these outer orbits determine the atom's chemical properties. > > > He was a physicist who was the first to apply the quantum theory > He recieved a Nobel Prize in 1922 for his work on the atomic structure and for physics.
 * [[image:bohr.jpg width="226" height="338" align="left"]]Born:** October 7, 1885

Planetary Model
The "planetary model" of the atom illustrated in the adjacent figure that, for example, is used as a symbol for atomic energy (a bit of a misnomer, since the energy in "atomic energy" is actually the energy of the nucleus, rather than the entire atom). In the Bohr Model the neutrons and protons (symbolized by red and blue balls in the adjacent image) occupy a dense central region called the nucleus, and the electrons orbit the nucleus much like planets orbiting the Sun (but the orbits are not confined to a plane as is approximately true in the Solar System).

Erwin Schrodinger-1877-1961

Born: August 12, 1887 Country Of Origin: Austria

Played a role in development of quantum mechanics, along with good friends Neils Bohr and Albert Einstein.

James Chadwick-1891-1974

Born:October 20, 1891 Country of Origin: England

In 1932, Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of //neutrons// particles that had no electrical charge. In contrast with the rays which are charged, and therefore repelled by the considerable electrical forces present in the nuclei of heavy atoms, this new tool in taking about atoms needed not to be overcome by 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.

He was awarded Nobel Prize for Physics in 1935.

Electron Cloud Model

The cloud model represents a sort of history of where the electron has probably been and where it is likely to be going. The red dot in the middle represents the nucleus while the red dot around the outside represents an instance of the electron. Imagine, as the electron moves it leaves a trace of where it was. This collection of traces quickly begins to resemble a cloud. The probable locations of the electron predicted by Schr�dinger's equation happen to coincide with the locations specified in Bohr's model.

Bibliography

__ Websites __ Introductory Chemistry, by Nivaldo J. Tro - Third Edition http://www.lucidcafe.com/library/95oct/nbohr.html http://www.crystalinks.com/bohr.html http://chemistry.learnhub.com/lesson/page/3674-history-of-the-atomic-theory-i-ancient-times http://www.philosophypages.com/hy/2n.htm#causes http://northspringer.tripod.com/HistoryofAtom/id1.html http://cti.itc.virginia.edu/~meg3c/classes/tcc313/200Rprojs/lavoisier2/home.html http://www.nndb.com/people/965/000100665/ http://nobelprize.org/nobel_prizes/physics/laureates/1901/rontgen-bio.html http://nobelprize.org/nobel_prizes/physics/laureates/1903/becquerel-bio.html http://nobelprize.org/nobel_prizes/physics/laureates/1903/marie-curie-bio.html http://nobelprize.org/nobel_prizes/physics/laureates/1923/millikan-bio.html http://www.aip.org/history/gap/Millikan/Millikan.html [|**http://images.google.com/imgres?imgurl=http://www.hasdeu.bz.edu.ro/softuri/fizica/mariana/Atomica/Models/cloud.gif&imgrefurl=http://www.hasdeu.bz.edu.ro/softuri/fizica/mariana/Atomica/Models/cloud.htm&h=200&w=200&sz=5&hl=en&start=7&um=1&usg=__FkV8B_CivIa-CA_J-uCT2iqIsww=&tbnid=yvdS8MpICjlZdM:&tbnh=104&tbnw=104&prev=/images%3Fq%3DElectron%2BCloud%2BModel%26um%3D1%26hl%3Den%26sa%3DN**]
 * http://nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html**

http://www.atomicarchive.com/Images/bio/B23.jpg http://www.crystalinks.com/bohr.html http://farm3.static.flickr.com/2297/2176802598_87acd63c24.jpg http://ec.europa.eu/education/img/flags/canada.gif http://www.geocities.com/joek_bm/images/matematica/biografias/foto_matematicos/Aristotle.jp [|**http://www.elektromania.net/images/F96D9_john_dalton7.jpg**] [|**http://usuarios.lycos.es/motorhidrogen/fotos_TDR/antoine_lavoisier.jpg**] [|**http://www.sciencefair-projects.org/images-sciencefair/chemistry/chemistry14.gif**] [|**http://www.dkimages.com/discover/previews/852/20223021.JPG**] [|**http://www.umw.edu/hisa/resources/Student%20Projects/Amy%20Miller%20--%20X-Ray/students.mwc.edu/_amill4gn/XRAY/pictures/crookstube.jpg**] [|**http://wwwlapp.in2p3.fr/neutrinos/centenaire/radimg/roentgen3.jpg**] [|**http://www.brynmawr.edu/Acads/Chem/mfrancl/PChemResource/404.jpg**] [|**http://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/Plum_pudding_atom.svg/348px-Plum_pudding_atom.svg.png**] [|**http://www.vias.org/physics/img/becquerel_plate.jpg**] [|**http://www.physics.umd.edu/courses/Phys420/Spring2002/Parra_Spring2002/Images/Physicists_Big/MarieCurie_Big.jpg**] [|**http://z.about.com/d/chemistry/1/0/v/T/curielab.jpg**] [|**http://www.wpclipart.com/famous/science/Ernest_Rutherford.png.html**] [|**http://www.nndb.com/people/771/000091498/robert-millikan-1.jpg**] [|**http://www.electro.patent-invent.com/electricity/images/oildropexperiment4.jpg**] [|**http://nobelprize.org/nobel_prizes/physics/laureates/1922/bohr.jpg**] [|**http://www.humanthermodynamics.com/schrodinger-photo_op_499x800.jpg**] [|**http://wwwlapp.in2p3.fr/neutrinos/neutimg/nacteurs/chadwick.jpg**]
 * __Photos__**