Group4

Group4 1/2 by Ellyn 1911 Lord Rutherford taught at the University of Manchester, England. Ernest Rutherford was head of a small scientific team, his two students Hans Geiger and Ernest Marsden. These were the scientists who originally carried out Rutherford’s experiments. Up until this point, scientists were largely using J.J Thompson’s atomic model, the “Plum Pudding Model.” Thompson’s research told us that atoms were in fact made up of tiny little particles called protons and electrons; one had negative charge, the other positive. What Thompson’s research didn’t tell us, was the placement of these particles throughout the atom; so Rutherford and his team began experimenting. Here’s what they figured: By shooting charged positive particles at a piece of gold foil (consisting of purely one type of atom) at high velocities, they would be able to track which particles bounced back; evidence of a highly charged area, a concentration of positives. After testing, they got results. They had set up a sheet of foil in front of a high-speed particle emitter, surrounded by a detecting screen. The screen’s purpose was to tell them the direction particles were bouncing; either passing straight through, or bouncing straight back. When the results were showing that particles really were bouncing backwards (even if the odds were 1 in 10 000), a little more research gave them the answer; Rutherford and his team had discovered the reason some particles had not passed right through; the nucleus, a massive concentration of positive charge in the center of the atom. Following his experiments, Rutherford was forced to replace Thompson’s model with his own, with more accuracy. His model insisted that the nucleus was centered in the atom, containing most of the mass of the atom. Surrounding the nucleus were electrons, but they hardly counted for much of the atom’s volume. Years later in 1932 another of Lord Rutherford’s students, James Chadwick, stated that as well as protons, the atom also contained neutral particles called neutrons. Chadwick’s research told us that each neutron in an atom had approximately the same mass as each proton in an atom.
 * GROUP SECTION: TIMELINE**
 * Ernest Rutherford**
 * WHEN**
 * WHERE**
 * WHO**
 * EXPERIMENTING**
 * THE ATOMIC MODEL**

Rutherford’s model had its strengths, as well as its weaknesses. His model clearly explained his theories; that the positive charge of an atom was focused in the middle, the electrons spread out surrounding it. What his model doesn’t tell us is how the electrons are placed, and how they orbit the nucleus without colliding with it; this was later answered by Niels Bohr in 1913.


 * REFERENCES**
 * "Rutherford's experiment and atomic model." The Worlds of David Darling. N.p., n.d. Web. 14 Sept. 2011. .
 * Hounjet, Camille, Bob Kvamme, Penny Mohr, Kelly Phillipchuk, and Ted View. //PEARSON Saskatchwean Science9//. Don Mills, ON: Reid McAlpine, 2011. Print.
 * "Rutherford model of the atom." //Indiana University Northwest//. N.p., n.d. Web. 28 Sept. 2011. .

__John Dalton (1803)__ __By. Nicole__ John Dalton's theory explained that all matter is made of small particales called atoms. Each element has their own type of atom. All atoms of the same element are identical. Elements are separated into different sizes based on the amount of "stuff" in the atom. It was after Dalton's time, when they discovered the "stuff" inside of each atom are actually protons, neutrons, electrons, and a nucleus. When atoms from two different elements are combined, they create a compound. However John Dalton's model and theory lacked essential information, such as, the existance of protons, neutrons, electrons and a nucleus. But it did include key information, such as, the atoms that make up an element are identical, and when two different elements are combined they create a compound. As for technology, there was not much Dalton could use in his time. However he did make use of the labratory equipment he did have, such as, the various pieces of glassware, and manometers for the measurement of gas pressures. Antoine Lavoisier helped developed Dalton's theory. Lavoisier designed a balancing device, which was used to prove that during a chemical reaction, there was no loss of mass. Lavoisier proved that something can't come from nothing. His device showed that the mass during a chemical reaction did not change, which led to the conclusion that atoms can not be created nor destroyed. Dalton's efforts lead to new ideas and a very rewarding future in science. __John Dalton's representation of carbon__ September, 24, 2011

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__John Dalton's Atomic Theory__ September, 26, 2011 []

__Antoine Lavoisier's Balancing Device__ Lavoisier created this balancing device to prove that during a chemical reaction, there is no loss of mass. The burning fire, which is a chemical reaction, has the same mass as an element that is not being chemically changed. October, 17, 2011

[] "Dalton Atomic Theory." //Royal Society of Chemistry, the largest organisation in Europe for advancing the chemical sciences.// N.p.,n.d.Wed.26 Sept.2011. [].
 * __References__**

"John Dalton's Model." //The Peking Man. N.p.,n.d. Wed. 26 Sept.2011.// //<http://northspringer.tripod.com//

"Early atomic history - Democritus, Lavoisier and Dalton." //Radioactivity and Electricity Teaching Resources | Furry Elephant//. N.p., n.d. Web. 17 Oct. 2011. [].

JJ Thomson (1897) Blayne Gallagher

In 1897, JJ Thomson discovered the electron. He used cathode rays and placed two electric plates in their path. One of the plates was of positive charge and the other was negative. The light particles in the cathode rays bent towards the positive charged plate. That showed the particles were negatively charged opposites attract. Thomson called the particles "corpuscles" but later were named electrons. After his discovery of the electron, Thomson suggested his own atomic theory. Thomson's theory was that an atom is a sphere shape, filled with a jelly-like positive charged substance. Electrons were scattered throughout the atom. Thomson stated atoms are neutrally charged, which means the negative and positive charges within the atom are equal. John Dalton believed atoms were "indivisible" and could not be destroyed or broken apart. Thomson proved that theory wrong when he removed electrons from an atom. This model was called the chocolate chip cookie model, or the plum pudding model. It was named this because the raisins in the pudding, and the chocolate chips in the cookie look very similar to the electrons in the atom. William Prout and Norman Lockeyer were two of the scientists who helped Thomson in his discovery of the electron and atomic theory. Ernest Rutherford was one of Thomson's students who later developed his own theory of an atom.



JJ Thomson's Model of an Atom

Strengths of the model: - Discovered electrons (1897) - Helped lead others to sucess (Rutherford) - Realized atoms are not indivisible

Weaknesses of the model: - Did not discover the nucleus - Did not involve protons or neutrons - His theory was disproved



"Google Images." //Google//. N.p., n.d. Web. 27 Sept. 2011. <http://www.google.ca/imgres?q=jj+thomson+model+of+an+atom&hl=en&biw=1024&bih=634&gbv=2&tbm=isch&tbnid=JFs2GTdHr82LyM:&imgrefurl=http://www.kentchemistry.com/links/AtomicStructure/JJThompson.htm&docid=-kBQ4ho5LxSejM&w=156&h=156// //"Plum pudding model - Wikipedia, the free encyclopedia."// Wikipedia, the free encyclopedia//. N.p., n.d. Web. 27 Sept. 2011. <http://en.wikipedia.org/wiki/Plu// //using. "Thomson Model (English)."// ±q¨wuÀ@ãBåwåw@w¤@¨wå//. N.p., n.d. Web. 27 Sept. 2011. <http://www.kutl.kyushu-u.ac.jp/seminar/MicroWorld1_E///

//**__Niels Bohr__**// //**__by Claire__**// //__Bohr Model:__// //@http://upload.wikimedia.org/wikipedia/commons/thumb/5/55/Bohr-atom-PAR.svg/310px-Bohr-atom-PAR.svg.png - 28/09/11//

//__Representation of Carbon:__// //@http://www.chemicalelements.com/bohr/b0006.gif//

// Discovered in 1913 by Niels Bohr, the Bohr model describes the atom as a small, positively charged nucleus outlined by electrons that revolve in circular motions around the nucleus—alike in structure to the solar system, but with electrostatic forces adding attraction, rather than gravity. The Bohr model is a quantum-physics–based modification of the Rutherford model, many sources join the two, calling it the Rutherford–Bohr model. // Bohr's discoveries based on Rutherford's model:

==== Rutherford and Bohr worked together on the model, imagining the arrangement of the atom's parts to look like the solar system. The reason behind that is in the middle of every atom is a nucleus, which is similar to the sun in the solar system. Also, the electrons moving around the nucleus in orbits is like the way plants revolve around the sun. ====
 * -** ** Electrons can move around the nucleus only in certain allowed orbits **
 * - They don't give off radiation when in these orbits **
 * - Each orbit has a certain quantity of energy **
 * - An electron can "jump" from one orbit to another **
 * - Moving in, energy is given off **
 * - Moving out, energy is absorbed **

==== However, the Bohr atom involved things that were hard to work with, like the radius of an orbit, because it could not be measured experimentally. In that case, Bohr's model was eventually replaced by a new theory based on wave mechanics. The crucial characteristic of Bohr's orbits, (for example, precise energy values) was still maintained in the new theory. ====

//**__References:__**// //"Bohr Model."// Wikipedia//. N.p., n.d. Web. 14 Sept. 2011. [-].// //"Bohr's Atom."// University of Colorado Boulder//. N.p., n.d. Web. 14 Sept. 2011. []// //"Bohr Model."// Upscale //. N.p., n.d. Web. 14 Sept. 2011. [|http://www.upscale.utoronto.ca/PVB/Harrison/BohrModel/BohrModel.html].// //"Bohr."// ThinkQuest//. N.p., n.d. Web. 26 Sept. 2011. []// //"Rutherford-Bohr Model | Radiation Protection | US EPA."// US Environmental Protection Agency//. N.p., n.d. Web. 26 Sept. 2011. []