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Atomic Structure

Courtesy of astronomyonline.org. Atomic Structure. Courtesy of hubpages.com. History of Atomic Structure. Famous Experiments/Models. J.J. Thomson's Plum Pudding model Raisins are the negatively charged particles(electrons)

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Atomic Structure

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  1. Courtesy of astronomyonline.org Atomic Structure Courtesy of hubpages.com

  2. History of Atomic Structure

  3. Famous Experiments/Models • J.J. Thomson's Plum Pudding model • Raisins are the negatively charged particles(electrons) • Electrons float in a pudding of positive charge (equal to negative charge) which makes neutral atom • Niels Bohr • Bohr model, shows electrons orbiting in specific energy shells (each shell containing a set electron limit) around nucleus • Robert Millikan • Found the mass of electron to be 1/1836 amu • Ernest Rutherford • Gold foil experiment • Alpha particles fired at gold. Some are deflected which proves a small dense nucleus in the center. J.J. Thomson’s model (top), Rutherford (bottom) Courtesy of en.wikipedia.org

  4. Protons • Positively charged subatomic particles in a atom • In a neutral atom # of protons= # of electrons • The positive charge and negative (electrons) charge should cancel each other out • Located in nucleus of atom along with neutrons • Mass of 1amu • Equal to the atomic number • Protons define which atom is which element • If # of protons change then it becomes a different element Courtesy of nasa.gov

  5. Neutrons • Subatomic particles with no charge • The mass of neutron nearly equals that of a proton (1amu) • Located in the nucleus of the atom • Protons and neutrons together in the nucleus equals the atom’s atomic mass • The nucleus is the most dense part of an atom for this reason Courtesy of about-chemistry.blogspot.com

  6. Electrons • Negatively charged subatomic particle • Surrounding nucleus is electron cloud • This is where electrons lie in specific orbital shells • Mass of 1/1836 amu, almost zero • The electron cloud accounts for very little of the atom’s mass • Ions are formed by loosing electrons (positive ion) and by gaining electrons (negative ions) Courtesy of greenenergybuild.com Courtesy of renesas.com

  7. Nucleus • The nucleus is in the center of the atom • Contains protons and neutrons • Almost all the mass is contained in the nucleus • Nucleus is very small compared to the actual atom • If the atom were the size of a stadium the nucleus would be a marble • Nucleus is very dense • A nucleus the size of a pea would weigh 250 tons Courtesy of www.safetyoffice.uwaterloo.ca

  8. Elements/Atomic Numbers/Mass • Atomic number is the number of protons in a atom • Protons = electrons in a neutral atom • The periodic table is ordered by atomic numbers • Mass=protons + neutrons Courtesy of msu.edu

  9. Isotopes • Isotopes are atoms of the same element with different neutrons and atomic mass • For example: Carbon is mostly found with 6 protons and 6 neutrons (Carbon-12) • Carbon can also have 7 neutrons (C-13) or 8 neutrons (C-14) although this happens more rarely • To calculate avg. atomic mass of element • (isotope # 1 total mass)x(abundance in nature-percentage) • Repeat for each isotope and then add answers together to get avg. atomic mass Courtesy of radiation-scott.org

  10. Sources • Bowles, Richard. "Atomic Structure." Richard Bowles Website. N.p., 29 Sept.      2010. Web. 29 Sept. 2010. <http://richardbowles.tripod.com/chemistry/      structure/structure.htm>. • Buescher, Lee. "Atomic Structure Timeline." Lee Buescher's Science Lab.      Watertown High School, 2010. Web. 25 Sept. 2010.      <http://atomictimeline.net/index.php>. • Carpi, Anthony. "Atomic Structure." The Natural Science Pages. N.p., 1999. Web.      25 Sept. 2010. <http://web.jjay.cuny.edu/~acarpi/NSC/3-atoms.htm>. • Wilbraham, Antony C., Dennis D. Staley, and Michael S. Matta. "Atomic Structure." Chemistry. Expanded 4th ed. Menlo Park: Addison-Wesley , 1997.      82-106. Print. Courtesy of mrjarretwalker.blogspot.com Courtesy mrstrong.wikis.msad52.org

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