2. Chapter 2 Atoms, Molecules, and Ions

3. History n Greek philosophers n Democritus and Leucippus - atomos n Aristotle- 4 elements: Earth, Air, Fire, and Water. n 1660 - Robert Boyle- experimental definition of element. n Lavoisier- Father of modern chemistry n He wrote the book- used measurement

4. Laws n Conservation of Mass- the total mass of materials present after a chemical reaction is the same as the total mass present before the reaction. n Law of Definite Proportion- compounds have a constant composition by mass. n They react in specific ratios by mass. n Multiple Proportions- When two elements form more than one compound, the ratios of the masses of the second element that combine with one gram of the first can be reduced to small whole numbers.

5. What?! n Water has 8 g of oxygen per g of hydrogen. n Hydrogen peroxide has 16 g of oxygen per g of hydrogen. n 16/8 = 2/1 n Small whole number ratios

6. Dalton’s Atomic Theory n 1. Elements are made up of atoms n 2. Atoms of each element are identical. Atoms of different elements are different. n 3. Compounds are formed when atoms combine. Each compound has a specific number and kinds of atom. n 4. Chemical reactions are rearrangement of atoms. Atoms are not created or destroyed.

7. n Gay-Lussac- under the same conditions of temperature and pressure, compounds always react in whole number ratios by volume. n Avagadro- interpreted that to mean:at the same temperature and pressure, equal volumes of gases contain the same number of particles. n (called Avagadro’s hypothesis) A Helpful Observation

8. Experiments to determine what an atom was n J. J. Thomson- used Cathode ray tubes

9. Thomson’s Experiment Voltage source +-

10. Thomson’s Experiment Voltage source +-

11. Thomson’s Experiment Voltage source +-

12. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

13. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

14. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

15. n Passing an electric current makes a beam appear to move from the negative to the positive end Thomson’s Experiment Voltage source +-

16. Thomson’s Experiment n By adding an electric field

17. Voltage source Thomson’s Experiment n By adding an electric field + -

18. Voltage source Thomson’s Experiment n By adding an electric field + -

19. Voltage source Thomson’s Experiment n By adding an electric field + -

20. Voltage source Thomson’s Experiment n By adding an electric field + -

21. Voltage source Thomson’s Experiment n By adding an electric field + -

22. Voltage source Thomson’s Experiment n By adding an electric field he found that the moving pieces were negative + -

23. Thomsom’s Model n Found the electron n Couldn’t find positive (for a while) n Said the atom was like plum pudding n A bunch of positive stuff, with the electrons able to be removed

24. Millikan’s Experiment Atomizer Microscope - + Oil

25. Millikan’s Experiment Oil Atomizer Microscope - + Oil droplets

26. Millikan’s Experiment X-rays X-rays give some drops a charge by knocking off electrons

27. Millikan’s Experiment +

28. They put an electric charge on the plates + + --

29. Millikan’s Experiment Some drops would hover + + --

30. Millikan’s Experiment + ++ +++++ -- -----

31. Measure the drop and find volume from 4/3πr 3 Find mass from M = D x V + + --

32. Millikan’s Experiment From the mass of the drop and the charge on the plates, he calculated the charge on an electron + + --

33. Radioactivity n Discovered by accident n Bequerel n Three types –alpha- helium nucleus (+2 charge, large mass) –beta- high speed electron –gamma- high energy light

34. Rutherford’s Experiment n Used uranium to produce alpha particles n Aimed alpha particles at gold foil by drilling hole in lead block n Since the mass is evenly distributed in gold atoms alpha particles should go straight through. n Used gold foil because it could be made atoms thin

35. Lead block Uranium Gold Foil Florescent Screen

36. What he expected

37. Because

38. Because, he thought the mass was evenly distributed in the atom

39. What he got

40. How he explained it + n Atom is mostly empty n Small dense, positive piece at center n Alpha particles are deflected by it if they get close enough

41. +

42. Modern View n The atom is mostly empty space n Two regions n Nucleus- protons and neutrons n Electron cloud- region where you have a chance of finding an electron

43. Sub-atomic Particles n Z - atomic number = number of protons determines type of atom n A - mass number = number of protons + neutrons n Number of protons = number of electrons if neutral

44. Symbols X A Z Na 23 11

45. Chemical Bonds n The forces that hold atoms together n Covalent bonding - sharing electrons n makes molecules n Chemical formula- the number and type of atoms in a molecule n C 2 H 6 - 2 carbon atoms, 6 hydrogen atoms, n Structural formula shows the connections, but not necessarily the shape.

46. H H HH H HCC n Structural Formula

47. n There are also other model that attempt to show three dimensional shape n Ball and stick n Space Filling

48. Ions n Atoms or groups of atoms with a charge n Cations- positive ions - get by losing electrons(s) n Anions- negative ions - get by gaining electron(s) n Ionic bonding- held together by the opposite charges n Ionic solids are called salts

49. Polyatomic Ions n Groups of atoms that have a charge n Yes, you have to memorize them. n List on separate handout.

50. Periodic Table

51. Metals n Conductors n Lose electrons n Malleable and ductile

52. Nonmetals n Brittle n Gain electrons n Covalent bonds

53. Semi-metals or Metalloids

54. Alkali Metals

55. Alkaline Earth Metals

56. Halogens

57. Transition metals

58. Noble Gases

59. Inner Transition Metals

60. +1+2-2-3

61. Naming compounds n Two types n Ionic - metal and non metal or polyatomics n Covalent- we will just learn the rules for 2 non-metals

62. Ionic compounds-basic rules n If the cation is monoatomic (made of one atom)- Name the metal (cation) just write the name. n If the cation is polyatomic (made of more than one atom)- name it Ex: Na 3 PO 4 Sodium Phosphate n If the anion is monoatomic- name it but change the ending to -ide n If the anion is poly atomic- just name it Ex: NaClSodium Chloride NH 4 ClAmmonium Chloride

63. Covalent compounds n Two words, with prefixes n Prefixes tell you how many. n mono (1), di (2), tri (3), tetra (4), penta (5), hexa (6), hepta (7), octa (8), nona (9), deca (10) n First element whole name with the appropriate prefix, except mono n Second element, -ide ending with appropriate prefix n Practice

64. More Naming

65. Ionic compounds--again n If the cation is monoatomic- Name the metal (cation) just write the name. n If the cation is polyatomic- name it n If the anion is monoatomic- name it but change the ending to -ide n If the anion is poly atomic- just name it n If the cation may have more than one charge, use the classic name or put a Roman numeral after the name of cation. Ex: FeO is Iron (II) oxide or Ferrous oxide

66. Ionic Compounds n Have to know the names of ions and whether they can have more than one charge, and have to know the polyatomic ions. n CaS nK2SnK2SnK2SnK2S n AlPO 4 n K 2 SO 4 n FeS n CoI 3

67. More Ionic Compounds n Fe 2 (C 2 O 4 ) n MgO n MnO n KMnO 4 n NH 4 NO 3 n Hg 2 Cl 2 n Cr 2 O 3

68. Ionic Compounds n KClO 4 n NaClO 3 n YBrO 2 n Cr(ClO) 6

69. Naming Covalent Compounds n Two words, with prefixes n Prefixes tell you how many. n mono, di, tri, tetra, penta, hexa, septa, nona, deca n First element, whole name with the appropriate prefix, except mono n Second element, -ide ending with appropriate prefix n Practice

70. n CO 2 n CO n CCl 4 nN2O4nN2O4nN2O4nN2O4 n XeF 6 nN4O4nN4O4nN4O4nN4O4 n P 2 O 10 Naming Covalent Compounds

71. Writing Formulas n Two sets of rules, ionic and covalent n To decide which to use, decide what the first word is. n If is a metal or polyatomic use ionic. n If it is a non-metal use covalent

72. Ionic Formulas n Charges must add up to zero n get charges from table, name of metal ion, or memorized from the list n use parenthesis to indicate multiple polyatomics

73. Ionic Formulas n Sodium nitride n sodium- Na is always +1 n nitride - ide tells you it comes from the periodic table (it is monoatomic) n nitride is N -3

74. Ionic Formulas n Sodium nitride n sodium- Na is always +1 n nitride - ide tells you it comes from the table n nitride is N -3 n doesn’t add up to zero Na +1 N -3

75. Ionic Formulas n Sodium nitride n sodium- Na is always +1 n nitride - ide tells you it comes from the table n nitride is N -3 n doesn’t add up to zero n Need 3 Na Na +1 N -3 Na 3 N

76. Ionic Compounds n Sodium sulfite n calcium iodide n Lead (II) oxide n Lead (IV) oxide n Mercury (I) sulfide n Barium chromate n Aluminum hydrogen sulfate n Cerium (IV) nitrite

77. Covalent compounds n The name tells you how to write the formula n duh n Sulfur dioxide n diflourine monoxide n nitrogen trichloride n diphosphorus pentoxide

78. More Names and formulas

79. Acids n Substances that produce H + ions when dissolved in water n All acids begin with H n Two types of acids n Oxyacids n non oxyacids

80. Naming acids n If the formula has oxygen in it n write the name of the anion, but change –ate to -ic acid –ite to -ous acid n Watch out for sulfuric and sulfurous n H 2 CrO 4 n HMnO 4 n HNO 2

81. Naming acids n If the acid doesn’t have oxygen n add the prefix hydro- n change the suffix -ide to -ic acid n HCl nH2SnH2SnH2SnH2S n HCN

82. Formulas for acids n Backwards from names n If it has hydro- in the name it has no oxygen n anion ends in -ide n No hydro, anion ends in -ate or -ite n Write anion and add enough H to balance the charges.

83. Formulas for acids n hydrofluoric acid n dichromic acid n carbonic acid n hydrophosphoric acid n hypofluorous acid n perchloric acid n phosphorous acid

84. Hydrates n Some salts trap water crystals when they form crystals n these are hydrates. n Both the name and the formula needs to indicate how many water molecules are trapped n In the name we add the word hydrate with a prefix that tells us how many water molecules

85. Hydrates n In the formula you put a dot and then write the number of molecules. Calcium chloride dihydrate = CaCl 2  2  Calcium chloride dihydrate = CaCl 2  2  Chromium (III) nitrate hexahydrate = Cr(NO 3 ) 3  6H 2 O Chromium (III) nitrate hexahydrate = Cr(NO 3 ) 3  6H 2 O