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Development of the Structure of the Atom

Development of the Structure of the Atom. Who studied the atom?. Democritus (400 BC) – early, logical atom theory John Dalton (1803) – early experimental atomic theory J.J. Thomson (1897) – electrons Eugen Goldstein (1886) – positively charged particles

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Development of the Structure of the Atom

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  1. Development of the Structure of the Atom

  2. Who studied the atom? • Democritus(400 BC) – early, logical atom theory • John Dalton (1803) – early experimental atomic theory • J.J. Thomson (1897) – electrons • Eugen Goldstein (1886) – positively charged particles • Robet Millikan – mass & charge of electrons

  3. Ernest Rutherford (1911) – nucleus • Niels Bohr (1911) – energy levels • Ernest Rutherford (1918) – protons • Erwin Schrödinger (1926) – probability equation • Werner Heisenberg (1927) – uncertainty principle • James Chadwick (1932)– neutrons

  4. Democritus “atomos” - tiny indivisible particles

  5. Dalton’s Atomic Theory All matter is composed of tiny, indivisible particles called atoms. Atoms of a given element are identical; atoms of different elements have different properties. When atoms of different elements combine to form compounds, they do so in simple, whole-number ratios. Atoms cannot be created nor destroyed.

  6. Thomson “Plum Pudding” Model • cathode rays • http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::100%25::100%25::/sites/dl/free/0072512644/117354/01_Cathode_Ray_Tube.swf::Cathode%20Ray%20Tube - positive sphere of matter with negative electrons embedded in it

  7. Eugen Goldstein canal rays or anode rays - positively charged particles fm gases

  8. Millikan’s Oil Drop Experiment Robert Millikan - determined the charge and mass of the electron

  9. RutherfordModelDiscovery of the Nucleus (Gold Foil Exp’t) http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf Much of the atom is empty space. The nucleus has a diameter 10,000 times smaller than the atom. http://web.visionlearning.com/custom/chemistry/animations/CHE1.2-an-atoms.shtml

  10. Bohr Model(Planetary Model) http://www.upscale.utoronto.ca/PVB/Harrison/BohrModel/Flash/BohrModel.html “quanta” (Max Planck) – E can be absorbed or released only in specific amounts

  11. Schrödinger – wrote a mathematical equation to describe the location & E of an electron in a H atom

  12. Heisenberg “Uncertainty Principle” The position and momentum of moving objects (like electrons) can’t both be known at the same time

  13. Quantum Mechanical Model • Currently accepted atomic theory • Based on the probability of finding electrons of given energy (electron cloud model) • http://www.regentsprep.org/regents/physics/phys05/catomodel/cloud.htm

  14. Summary Table of Atomic Models http://www.clickandlearn.org/Gr9_Sci/atoms/modelsoftheatom.html#Bohr-Rutherford

  15. What is the structure of an atom? • Nucleus – center of the atom • Home of Protons and Neutrons • Proton • Has a positive (+) charge • Has a relative mass of 1 • Determines the atomic number • Found inside the nucleus p+

  16. Neutron • Has no (0) charge • Has a relative mass of 1 • Determines the isotope • Isotopes are two of the same element with different masses (same no. of protons but different number of neutrons) • Found inside the nucleus no

  17. Electron • Has a negative (-) charge • Has a relative mass of 1/1840 • Determines the ion • Found outside the nucleus • Bohr model – electrons are in specific energy levels • Electron cloud model – the probability of finding the electrons is called an electron cloud e-

  18. Subatomic Particles • Protons and electrons are the only particles that have a charge. • Protons and neutrons have essentially the same mass. • The mass of an electron is so small we ignore it.

  19. Actual Charge and Mass of Subatomic Particles Mass of an electron = 9.101 x 10-31kg Mass of a proton = 1.673 x 10-27kg Mass of a neutron = 1.675 x 10-27kg charge of an electron = -1.602 x 10-19 coulombs charge of a proton = +1.602 x 10-19 coulombs

  20. Atomic Number, Mass Number, Ions • # protons = atomic number (ID) • # electrons = # protons (neutral atom) • # protons + # neutrons = mass number

  21. Atomic Number All atoms of the same element have the same number of protons = atomic number (Z)

  22. Mass Number mass number = total number of protons and neutrons

  23. 11 6 12 6 13 6 14 6 C C C C Isotopes • Atoms of the same element with different masses. • Isotopes have different numbers of neutrons.

  24. Isotopes of Hydrogen

  25. Isotopes http://web.visionlearning.com/custom/chemistry/animations/CHE1.3-an-isotopes.shtml

  26. Average Mass • Because in the real world we use large amounts of atoms and molecules, we use average masses in calculations. • Average mass is calculated from the isotopes of an element weighted by their relative abundances.

  27. Other Subatomic Particles http://education.jlab.org/atomtour/listofparticles.html http://www.pbs.org/wgbh/nova/diamond/insidewave.html

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