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Structure of the Atom

Structure of the Atom

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Structure of the Atom

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  1. Structure of the Atom Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

  2. + - Cathode Ray Tube Turn the field on & off by clicking on the + & - Heated cathodes emitted cathode "rays" Deflected by either magnetic or electric fields J.J. Thomson, 1897

  3. + - J. J. THOMSON (1897)British Physicist The "beam" carried a negative charge. How did he know that? The ratio of charge to mass (e/m) was independent of the cathode material. Why does this indicate that cathode rays (electrons) are an integral part of each element?

  4. 2000 K Intensity ® 1800 K 1300 K 1000 3000 5000 Wavelength (nm) Blackbody Radiation In fact, the intensity peaked and then dropped off. According to classical theory, the intensity of black body radiation should be related to wavelength.

  5. 2000 K Intensity ® 1800 K 1300 K 1000 3000 5000 Wavelength (nm) Blackbody Radiation This failure of theory in the ultraviolet region of the spectrum, was called the "Ultraviolet Catastrophe”. It implied that the energies in an atom are limited or quantized. Based on this, Max Planck (1901, German Physicist) developed a quantum theory that electrons in an atom can have only specific energies.

  6. - + Photoelectric Effect Albert Einstein (1905)German Physicist Interpreted the Photoelectric Effect Confirmed that light is corpuscular (possess particle-like properties) Blue Red Light Source Light Source Light Source

  7. + - Oil Drop Experiment Robert Millikin (1909)American Physicist Determined the absolute charge of an electron (4.8 x 10–10 esu)

  8. Gold Foil Experiment(»10-4 cm thick) Kotz & Purcell (1987) Rutherford, 1911

  9. Ernest Rutherford (1911)British Chemist Most of the alpha particles (a, 4He2+) passed straight through, but a few were deflected or reflected straight backwards. Since alpha particles were known to have a positive charge, this indicated that the nucleus of an atom contained most of the mass, and that it was positive in charge Diagram source unknown

  10. Niels Bohr (1913)(Danish Physicist) • Postulated that electrons spin around the nucleus in an orbit. The energy differences between these orbits can be used to explain the various colors of light emitted and absorbed by gaseous elements.

  11. Henry Moseley (1914)(British Physicist) • Developed a periodic table based on increasing atomic number. • Each element has an unique "spectra" (wavelengths or colors of light) that they emit when heated to glowing.

  12. a Energy ® Emission Spectra • The spectra contains many colors (wavelengths) which are not uniformly spaced. M band K band L band

  13. Atomic Inverse Ka Element Mass Number Sqrt(Ka) (Å) Li 6.94 3 226.6 0.066 Be 9.01 4 110.7 0.095 B 10.81 5 66.3 0.123 C 12.00 6 43.6 0.151 N 14.01 7 31.0 0.180 O 16.00 8 23.3 0.207 Development of the Periodic Table

  14. Ka Radiation of Light Weight Elements 2 R = 0.9951 0.25 0.20 0.15 1/sqrt(Ka) 0.10 0.05 0.00 5 10 15 20 Mass (amu)

  15. Integer Relationship of Ka Radiation 2 R = 1 0.25 0.20 0.15 1/sqrt(Ka) 0.10 0.05 0.00 2 4 6 8 10 Integers Atomic Number

  16. Erwin Schrodinger (1926)(Austrian Physicist) • Developed the modern view of the atom, treating electrons as mathematical functions. • sine and cosine wave functions. Louis de Broglie (1926)(French Physicist) • Proposed that matter has both wave and particle properties.

  17. James Chadwick (1932)(British Physicist) • Determined the existence of the uncharged neutron. • Neutrons reside along with protons in the nucleus and explain the fact that elements have isotopes.

  18. charge (protons & electrons) 19 F 9 mass number protons & neutrons atomic number (protons) Protons, Neutrons and Electrons Fluorine atom How many protons, neutrons and electrons are in a fluorine atom?

  19. charge (protons & electrons) mass number protons & neutrons atomic number (protons) Protons, Neutrons and Electrons Chloride ion 37 Cl– 17 How many protons, neutrons and electrons are in a chloride ion?

  20. Protons, Neutrons and Electrons Aluminum ion 27 Al3+ 13 How many protons, neutrons and electrons are in an aluminum ion?

  21. Using the Periodic Table • Monatomic ions (ions containing only one atom) often have a charge that can be derived directly from the periodic table.

  22. H O Li Be F Cl Na S Mg Al Ca Br K Cr Fe Ni Cu Zn Ti Mn As Co Sr I Rb Pd Ag Cd Sn Sb Pb Bi Hg Cs Ba Pt Tl Au +1 ions

  23. H O Li Be F Cl Na S Mg Al Ca Br K Cr Fe Ni Cu Zn Ti Mn As Co Sr I Rb Pd Ag Cd Sn Sb Pb Bi Hg Cs Ba Pt Tl Au +2 ions

  24. H O Li Be F Cl Na S Mg Al Ca Br K Cr Fe Ni Cu Zn Ti Mn As Co Sr I Rb Pd Ag Cd Sn Sb Pb Bi Hg Cs Ba Pt Tl Au +3 ions

  25. H O Li Be F Cl Na S Mg Al Ca Br K Cr Fe Ni Cu Zn Ti Mn As Co Sr I Rb Pd Ag Cd Sn Sb Pb Bi Hg Cs Ba Pt Tl Au -1 ions

  26. Coordination Compound Nomenclature Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

  27. Coordination Compounds • Metal ion • the central atom • Ligand • atom, ion or molecule bound to the metal The nomenclature of a salt and a coordination compound are different.

  28. Salt Nomenclature Fe3+ ion requires 3 Cl– FeCl3 iron(III) chloride Salt (ionic) nomenclature only indicates the stoichiometry of the compound.

  29. 3- Cl Cl Cl Fe Cl Cl Cl Coordination Compound Nomenclature Coordination compound nomenclature communicates the environment of the central ion. hexachloroferrate(III) ion the iron ion is coordinated to six chloride ligands

  30. H H 3+ H O H O O H H Fe H H O O O H H H H Coordination Compound Nomenclature Coordination compound nomenclature communicates the environment of the central ion. hexaaquairon(III) ion the iron ion is coordinated to six water ligands

  31. Nomenclature of Inorganic Coordination Compounds • Cation/anion sequence • Ligand names • Cationic/anionic complexes • Alphabetical sequencing • Brackets

  32. Name each of the following [Cu(NH3)2Cl2] diamminedichlorocopper(II) [Cu(NH3)4]2+ tetramminecopper(II) ion [CuCl4]2– tetrachlorocuprate(II) ion

  33. Nomenclature of Inorganic Coordination Compounds • What is the meaning of Roman numerals in parenthesis? • When is copper used and when is cuprate used? • Meaning of the words aqua, ammine, cyano, chloro, bromo, iodo? • Application of the prefixes di, tri, tetra, … • Order in which the words are used?

  34. + - Cathode Ray Tube Heated cathodes emitted cathode "rays" Deflected by either magnetic or electric fields J.J. Thomson, 1897

  35. - + Photoelectric Effect Albert Einstein (1905)German Physicist Interpreted the Photoelectric Effect Confirmed that light is corpuscular (possess particle-like properties)