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Modern Chemistry Chapter 3 Atoms: The Building Block of Matter

Modern Chemistry Chapter 3 Atoms: The Building Block of Matter. Mass number nuclide Atomic mass unit Average atomic mass Mole Avogadro’s number Molar mass. Chapter Vocabulary. Law of conservation of mass Law of definite proportions Law of multiple proportions Atom Nuclear forces

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Modern Chemistry Chapter 3 Atoms: The Building Block of Matter

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  1. Modern ChemistryChapter 3Atoms: The Building Block of Matter

  2. Mass number nuclide Atomic mass unit Average atomic mass Mole Avogadro’s number Molar mass ChapterVocabulary Law of conservation of mass Law of definite proportions Law of multiple proportions Atom Nuclear forces Atomic number Isotope

  3. Section 1 Atoms: From Philosophical Idea to Scientific Theory Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  4. Foundation of Chemical Atomic Theory • Law of Conservation of Mass • Mass is neither created nor destroyed during ordinary chemical reactions or physical changes Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  5. Law of Conservation of Mass Image p. 69* Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  6. Law of Conservation of Mass Image p. 69* Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  7. Foundation of Chemical Atomic Theory • Law of Definite Proportions • A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or the source of the compound. Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  8. Foundation of Chemical Atomic Theory • Law of Multiple Proportions • If two or more different compounds are composed of the same two elements then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers. Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  9. Law of Multiple Proportions Image p. 69* Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  10. Dalton’s Atomic Theory 1. All matter is composed of extremely small particles called atoms Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  11. Dalton’s Atomic Theory 2. Atoms of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass and other properties. Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  12. Dalton’s Atomic Theory 3. Atoms cannot be subdivided, created or destroyed. Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  13. Dalton’s Atomic Theory 4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds. Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  14. Dalton’s Atomic Theory 5. In chemical reactions, atoms are combined, separated or rearranged. Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  15. Modern Atomic Theory Leucippus Atomic Theory Tested by experiment and modified with new discoveries and experiments Democritus Chapter 3 Section 1 Atoms: Ideas to Theory pages 67-71

  16. Section 2 The Structure of the Atom Chapter 3 Section 2 The Structure of the Atom pages 72-76

  17. Discovery of the Electron • Cathode Ray Tube Experiment - Thompson • Observations • Cathode Rays are deflected a magnetic field. • Cathode rays are deflected from a negatively charged object. • Charge to mass ratio is always the same for the cathode rays. Chapter 3 Section 2 The Structure of the Atom pages 72-76

  18. Discovery of the Electron • Cathode Ray Tube Experiment - Thompson • Conclusion • Cathode rays are composed of negatively charged particles • Named “electrons” Chapter 3 Section 2 The Structure of the Atom pages 72-76

  19. Discovery of the Electron • Oil Drop Experiment - Millikan • Measured the charge of the electron • Calculated the mass of an electron • 9.109 x 10-31 kg Chapter 3 Section 2 The Structure of the Atom pages 72-76

  20. Discovery of the Electron • Inferences • Atoms are neutral, so there must be a positive charge. • Electrons are small, so there must be other particles. Chapter 3 Section 2 The Structure of the Atom pages 72-76

  21. Discovery of the Electron • Plum Pudding Model • Negative electrons were spread evenly throughout the positive charge. Chapter 3 Section 2 The Structure of the Atom pages 72-76

  22. Discovery of the Atomic Nucleus • Gold Foil Experiment – Rutherford et. al • Hypothesis: Alpha particles would pass through with slight deflection. • Observation: 1 in 8000 particles were deflected back to the source. • Conclusion: The atom contains a small densely packed bundle of matter with a positive charge • Named the “nucleus” Chapter 3 Section 2 The Structure of the Atom pages 72-76

  23. Gold Foil Experiment Image p. 75 Chapter 3 Section 2 The Structure of the Atom pages 72-76

  24. Discovery of the Atomic Nucleus Relative size of the nucleus Chapter 3 Section 2 The Structure of the Atom pages 72-76

  25. Composition of The Atomic Nucleus • Nuclei contain protons and neutrons • Neutral because number of protons equal number of electrons • Each element has a different number of protons in their nucleus • The number of protons determines the atom’s identity • Nuclear forces hold protons & neutrons together Chapter 3 Section 2 The Structure of the Atom pages 72-76

  26. Properties of Subatomic Particles p. 76 Chapter 3 Section 2 The Structure of the Atom pages 72-76

  27. Gold Foil Experiment Photo Chapter 3 Section 2 The Structure of the Atom pages 72-76

  28. Gold Foil Experiment Photo Chapter 3 Section 2 The Structure of the Atom pages 72-76

  29. Thompson and Rutherford Photo Chapter 3 Section 2 The Structure of the Atom pages 72-76

  30. Section 3 Counting Atoms Chapter 3 Section 3 Counting Atoms pages 77-87

  31. Atomic Number • The number of protons of each atom of that element • Identifies the element Chapter 3 Section 3 Counting Atoms pages 77-87

  32. Isotopes • Atoms of the same element that have different masses • Isotopes of hydrogen • Protium 1p+ 0n0 • Deuterium 1p+ 1n0 • Tritium 1p+ 2n0 • Isotopes do not differ significantly in their chemical behavior Chapter 3 Section 3 Counting Atoms pages 77-87

  33. Mass Numbers • Mass numbers = # of p+ + # of n0of a specific isotope • Examples • Protium 1p+ +0n0 = 1 • Deuterium 1p+ +1n0 = 2 • Tritium 1p+ +2n0 = 3 Chapter 3 Section 3 Counting Atoms pages 77-87

  34. 3 H mass number 1 atomic number Designating Isotopes • Hyphen notation • name of element – mass number • Hydrogen – 3 • Nuclear symbol Chapter 3 Section 3 Counting Atoms pages 77-87

  35. Number of neutrons in an atom neutrons = mass number – atomic number Problem page 77 How many p+, e- and n0 are there in an atom of chlorine-37? 17 p+ 17e- 20n0 (37-17) Practice Problems page 78 #1-3 Nuclide – a general term for a specific isotope of an element Chapter 3 Section 3 Counting Atoms pages 77-87

  36. Relative Atomic Mass • One atom, carbon-12, is set as a standard • All masses are expressed in relation to this standard • 1 atomic mass unit = 1/12 the mass of a carbon-12 atom Chapter 3 Section 3 Counting Atoms pages 77-87

  37. Relative Atomic Mass • Examples • Hydrogen – 1 = 1.007825 amu • Oxygen – 16 = 15.994915 amu • Magnesium – 24 = 23.985042 amu • p+ = 1.007276 amu, n0 = 1.008665 amu, e- = 0.0005486 amu • Relative mass and mass number are close in value but not the same Chapter 3 Section 3 Counting Atoms pages 77-87

  38. Average Atomic Mass • The weighted average of the atomic masses of naturally occurring isotopes of an element • AM = (mass isotope x abundance)+(mass isotope x abundance)+... • Example • CopperCu-63: .6915 x 62.93 amu = 43.52Cu-65: .3085 x 64.93 amu = 20.03 63.55 amu relative mass percent Chapter 3 Section 3 Counting Atoms pages 77-87

  39. The Mole • An amount of a substance that contains as many particles as there are atoms in exactly 12 g carbon-12. • Similar to a dozen or a pair or a gross • 6.022 x 1023 carbon-12 atoms = 12 grams of carbon-12 • Avogadro’s number = 6.022 x 1023 particles Chapter 3 Section 3 Counting Atoms pages 77-87

  40. Molar mass • The mass of one mole of a pure substance • Unit = g/mol • On the periodic table, use 4 sig. figs. Chapter 3 Section 3 Counting Atoms pages 77-87

  41. mol g g mol Gram-Mole Conversions • The conversion factor for gram-mole conversion is molar mass. • What is the mass, in grams, of 3.50 moles of Cu? • 222 grams Cu OR Chapter 3 Section 3 Counting Atoms pages 77-87

  42. Practice Problems page 85 126 g Fe 14.7 g K 0.310 g Na 957 g Ni • What is the mass in grams of 2.25 mol of the element iron? • What is the mass in grams of 0.357 mol of the element potassium? • What is the mass in grams of 0.0135 mol of the element sodium? • What is the mass in grams of 16.3 mol of the element nickel? p. 85 Chapter 3 Section 3 Counting Atoms pages 77-87

  43. Conversions Image p. 84 Chapter 3 Section 3 Counting Atoms pages 77-87

  44. mol g g mol Gram-Mole Conversions • The conversion factor for gram-mole conversion is molar mass. • A Chemist produced 11.9 g of Al. How many moles of Al were produced? • 0.411 moles Al OR Chapter 3 Section 3 Counting Atoms pages 77-87

  45. Practice Problems page 83 • How many moles of calcium are in 5.00 g of calcium? • How many moles of gold are in 3.60 x 10-5 g of gold? • How many moles of zinc are in 0.535 g of zinc? 0.125 mol Ca 1.83 x 10-7 mol Au 8.18 x 10-3 mol Zn p. 85 Chapter 3 Section 3 Counting Atoms pages 77-87

  46. 6.022x1023atoms 1 mol 1 mol 6.022x1023atoms Conversions with Avogadro’s Number • The conversion factor for particle-mole conversion is Avogadro’s number. • How many moles of silver are in 3.01 x 1023 atoms of silver • 0.500 moles Ag OR Chapter 3 Section 3 Counting Atoms pages 77-87

  47. Practice Problems page 84 • How many moles of lead are 1.50 x 1012 atoms of lead? • How many moles of tin are in 2500 atoms of tin? • How many atoms of aluminum are in 2.75 mol of aluminum? 2.49 x 10-12 mol Pb 4.2 x 10-21 mol Sn 1.66 x 1024 atoms Al p. xx Chapter 3 Section 3 Counting Atoms pages 77-87

  48. 6.022x1023atoms 1 mol 1 mol 6.022x1023atoms Conversions with Avogadro’s Number • The conversion factor for particle-mole conversion is Avogadro’s number. • What is the mass, in grams, of 1.20x1018 atoms of Cu? • 1.27 x 10-4 g Cu OR Chapter 3 Section 3 Counting Atoms pages 77-87

  49. Practice Problems page 85 • What is the mass in grams of 7.5 x 1015 atoms of nickel? • How many atoms of sulfur are in 4.00 g of sulfur? • What mass of gold contains the same number of atoms as 9.0 g of aluminum? 7.3 x 10-7 g Ni 7.51 x 1022 atoms S 66 g Au p. xx Chapter 3 Section 3 Counting Atoms pages 77-87

  50. Conversions Image p. 84 Chapter 3 Section 3 Counting Atoms pages 77-87

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