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460
Democritus (460 BC)
Discovered that everything is made up of atoms. He said,"The more any indivisable exceeds, the heavier it is."emocritus developed the atomic theroy by using experiments and guessing to come up the theory of the atom. Democritus never developed his own model of what an aotm looked like because he thought atoms were invisable tiney particles."Democritus - Biography." Democritus. The European Graduate School, n. d. Web. 25 Feb. 2014 -
Dalton
Dalton developed the atomic theory of matter in which he said tha teverything that occupies space and has mass is matter. He also theorized that atoms are extreamly small particals and all atoms of an element have the same mass. To come up with his theories, Dalton oreformed experiments with various chemicals that showed matter, and seemed to consist of elementart atoms. Dalton Atomic Model. N.d. Photograph. Quia. Web. 27 Feb
"Dalton, John" World Book Discovery. World Book, 2014. Web. 27 Feb.2014 -
Thomson and Electrons
Thomson used experiments with cathod ray tubes that showed the cathod rays had a negative charge and were always identical no matter what the nature of the ectrodes or gas used. The canal rays' which had a positive charge, were different when different gasses were used. This proved his theory that atoms have negatively charged electrons, but the atom's had a large body with a positive charge.Harvey, Nicole. "Unit 5: Concept 2." 6th Hour Physical Science Honors. United States, Zachary. 26 Feb. 20 -
Plum Pudding Model
Thomson suggested a model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces. Thomson also had the theory that electrons were negatively charged based off of his experiments with cathod ray tubes that showed the cathod rays( which were negatively charged) were always identical regardless of the nature the ectrodes or gas used.
"Bio.com." Bio.com. A&E Networks Television, n.d. Web. 27 Feb. 2014. -
Rutherford and Investigating the Atom
Rutherford bombarded atoms with alpha rays by using radium as the source of alpha particles and shined it onto the atoms in the gold foil experiment.
Rutherford-atomic Theory." Royal Society of Chemistry | Advancing Excellence in the Chemical Sciences. N.p., n.d. Web. 23 Feb. 2014.
Ruerford's Atom. N.d. Photograph. Http://www.iun.edu/. Rutherford Planetary Model of the Atom. Web. 25 Feb. 2014 -
Rutherford Discovers the Atomic Nucleus
Rutherford used the Gold Foil experiment to make his discoveries. The experiment involved firing radioactive particles through extreamly thin foils of metal which were notably gold. and detecting the particles usign screens coated with zin sulfied. He found that although many of the particles passed through the foil, about 1/8000 were deflected, leading him to his theory that the atom was mostly empty space. -
Borh and the Atom
Bohr developed the theory that protons are in the nucleus and electrons surround it. He believed that electrons can only move in certain paths and outer electrons(valence electrons) determine the elements' chemical property. Bohr expanded on Rutherford's theory. Bohr's model of the atom showed the total electron configuration and placed electrons on rings. His experiments showed his model had some troubles.
"Bohr Atomic Model." Encyclopedia Britannica, n.d. Web. 25
picture also from same site. -
The discovery of the Proton
Rutherford identified that particles of the nucleus as discrete positive charges of matter, named them protons, and found that protons' mass was about 1,800 times greater than the mass of an electron. His model, "The Atomic Planetary Model" showed that most of the mass of an atom is located in the nucleus.
"Rutherford-atomic Theory." Royal Society of Chemistry | Advancing Excellence in the Chemical Sciences. N.p., n.d. Web. 23 Feb. 2014. -
Heisenberg and Schrodinger
Schrodinger thought to model the atom as a wave that vibrates in a circle. Heinsenburg based his theory off of mathmatical quantities called matrices, that fit with the conception of electrons as particles. Results of both appeared mathematically correct, "Heisenburg's uncertainty principle" said no experiment can measure location and quantum particle simultaneously. The two scientists made the electron cloud model.Harvey, Nicole. "Unit 5: Concept 2." 6th Hour Physical Science Honors. U.S.A. -
Aristotle(348 BC)
Aristotle rejected the atomic theory. He pointed out that modern theologians were more detached from eccelsiasticlal power politics so it would not be neccesary for them to defend anachronisms. Aristotal thought the atomic theory had no merit and dismissed the theory as worthless.He came to this conclusion by the study of truth and seeking to understand the mysteries of exsistence.
Walker, Jim."History of Atoms." History of Atoms The Atoms' Hyper Card, Nov. 2004. Web. 26 Feb. 2014.
