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Atoms, Molecules, and Ions

Atoms, Molecules, and Ions. Atomic Theory. Robert Boyle (1627–1691) Joseph Priestley (1733–1804) Antoine Lavoisier (1743–1794) Joseph Proust (1754–1826) John Dalton (1766-1844). Robert Boyle.

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Atoms, Molecules, and Ions

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  1. Atoms, Molecules, and Ions

  2. Atomic Theory • Robert Boyle (1627–1691) • Joseph Priestley (1733–1804) • Antoine Lavoisier (1743–1794) • Joseph Proust (1754–1826) • John Dalton (1766-1844)

  3. Robert Boyle • Robert Boyle (1627–1691): Provided evidence for the atoms and defined the nature of an element. More than anyone else, invented the modern experimental method.

  4. Joseph Priestly • Joseph Priestley (1733–1804): Isolated oxygen gas from decomposition of mercury(II) oxide. Identified 8 new gases (more than anyone else). Minister. Revolutionary.

  5. Antoine Lavoisier Antoine Lavoisier (1743–1794): Showed that mass of products is exactly equal to the mass of reactants. Father of modern chemistry. Metric system. Beheaded during the revolution.

  6. Conservation of Mass

  7. Conservation of Mass

  8. Atomic Theory • Law of Mass Conservation: Mass is neither created nor destroyed in chemical reactions. • Law of Definite Proportions: Different samples of a pure chemical substance always contain the same proportion of elements by mass.

  9. Joseph Louis Proust Joseph Louis Proust (1754–1826): Proved the law of definite proportions (sometimes called Proust’s Law). Father was an apothecary. Discovered 3 vegetable sugars.

  10. Law of Definite Proportions

  11. Atomic Theory • Nitrogen & oxygen combine to form NO or NO2: • In NO the N:O mass ratio is 7:8 • In NO2 the N:O mass ratio is 7:16 • Hydrogen & oxygen combine to form H2O or H2O2: • In H2O the H:O mass ratio is 1:8 • In H2O2 the H:O mass ratio is 1:16

  12. Dalton’s Atomic Theory • John Dalton (1766–1844): Proposed explanations for the laws of mass conservation and definite proportions. Provided a unified atomic theory. Avid meteorologist. Worked with Nitrous Oxide and Nitrogen Dioxide.

  13. Law of Multiple Proportions

  14. Dalton’s Atomic Theory • John Dalton (1766–1844): Proposed explanations for the laws of mass conservation and definite proportions. Postulate #1 • Elements are composed of tiny particles called atoms

  15. Dalton’s Atomic Theory • John Dalton (1766–1844): Proposed explanations for the laws of mass conservation and definite proportions. Postulate #2 • All atoms of a given element are identical having the element’s unique properties

  16. Dalton’s Atomic Theory • John Dalton (1766–1844): Proposed explanations for the laws of mass conservation and definite proportions. Postulate #3 • Atoms are neither created nor destroyed in chemical reactions

  17. Dalton’s Atomic Theory • John Dalton (1766–1844): Proposed explanations for the laws of mass conservation and definite proportions. Postulate #4 • Compounds are formed when atoms of more than one elenment combine. A given compound always has the same relative numbe of atoms

  18. Dalton’s Atomic Theory

  19. Dalton’s Atomic Theory • Law of Multiple Proportions: • When two elements form two different compounds, the mass ratios are related by small whole numbers.

  20. Law of Multiple Proportions

  21. Dalton’s Atomic Theory • Methane and ethane are both constituents of natural gas. A sample of methane contains 11.40 g of carbon and 3.80 g of hydrogen, whereas a sample of ethane contains 4.47 g of carbon and 1.118 g of hydrogen. Show that the two substances obey the law of multiple proportions.

  22. The Structure of Atoms

  23. The Structure of Atoms

  24. The Structure of Atoms • Cathode-Ray Tube (Thomson, 1856–1940): • Cathode raysconsist of tinynegativelycharged particles, now calledelectrons.

  25. The Structure of Atoms

  26. The Structure of Atoms • Deflection of electron depends on three factors: • Strength of electric or magnetic field • Size of negative charge on electron • Mass of the electron • Thomson calculated the electron’s charge to mass ratio as 1.758820 x 108 Coulombs per gram.

  27. The Structure of Atoms • Oil Drop Experiment (Millikan, 1868–1953): Applied a voltage to oppose the downward fall of charged drops and suspend them. • Voltage on plates place 1.602176 x 10-19 C of charge on each oil drop. • Millikan calculated the electron’s mass as 9.109382 x 10-28 grams.

  28. The Structure of Atoms

  29. The Structure of Atoms • Discovery of Nucleus (Rutherford, 1871 – 1937): • Rutherford irradiatedgold foil with a beamof alpha () particlesto search for positivecharged particles.

  30. The Structure of Atoms

  31. The Structure of Atoms Discovery of Nucleus (Rutherford, 1871–1937): Rutherford irradiatedgold foil with a beamof alpha () particlesto search for positivecharged particles. Atom must be mostly empty space except for a central positive mass concentration.

  32. The Structure of Atoms

  33. The Structure of Atoms

  34. The Structure of Atoms • Structure of the Atom:

  35. The Structure of Atoms

  36. The Structure of Atoms Atomic Mass Unit 1 amu = 1/12 of the mass of on atom of Carbon-12 1 amu = 1.6605 x 10-24 g

  37. The Structure of Atoms • Isotopes: Atoms with identical atomic numbers, but different mass numbers. • Atomic Mass: A weighted average of the isotopic masses of an element’s naturally occurring isotopes.

  38. 75 75 Se Se 34 34 The Structure of Atoms • The isotope is used medically for diagnosis of pancreatic disorders. How many protons, neutrons, and electrons does an atom of have? • An atom of element X contains 47 protons and 62 neutrons. Identify the element, and write the symbol for the isotope in the standard format.

  39. 37 35 Cl Cl 17 17 The Structure of Atoms • Chlorine has two naturally occurring isotopes: with an abundance of 75.77% and an isotopic mass of 34.969 amu, and with an abundance of 24.23% and an isotopic mass of 36.966 amu. What is the atomic mass of chlorine?

  40. The Structure of Atoms

  41. Compounds and Mixtures

  42. Ions • Electrically charged atom or group of atoms • Cation: (+) charge • Anion: (-) charge • Ionic Compound: A compound that consists of ions

  43. Ions

  44. Ions

  45. Atoms, Molecules, and Ions

  46. Atoms, Molecules, and Ions

  47. Naming Cations 1. Elements having just one characteristic ionic charge Simply use the name of the element: Na+ sodium ion Zn2+ zinc ion K+ potassium ion Al3+ aluminum ion Ca2+ calcium ion etc.

  48. Naming Cations 2. Elements forming more than one type of cation Follow the name of the element with its stock number (Roman numeral equal to the number of electrons lost): Fe2+ iron (II) ion Pb2+ lead (II) ion Fe3+ iron (III) ion Pb4+ lead (IV) ion

  49. Naming Anions Stem + ide F- fluoride Cl- chloride Br- bromide O2- oxide S2- sulfide N3- nitride

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