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CHAPTER 9: CHEMICAL NAMES AND FORMULAS Sections 1-5 (Read pages 252-285) 1.

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1 CHAPTER 9: CHEMICAL NAMES AND FORMULAS Sections 1-5 (Read pages ) 1

2 Chapter 9 Vocab  Acid  Base  Binary compound  Law of definite proportions  Law of multiple proportions  Monatomic ion  Polyatomic ion 2

3 Read pages Section 9.1: Naming Ions

4 Monatomic Ions  Ions that consist of a single atom with a positive or negative charge resulting from the loss or gain of one or more valence electrons  Two Types  Positive Ions Cations  Negative Ions Anions 4

5 Cations  Positively charged ions  Metal atom loses electrons  Name stays the same Example: Name of Element: Aluminum Number of Valence Electrons: 3 Charge on Ion: +3 Name of Ion: Aluminum 5

6 Naming Cations Practice Element# of Valence Electrons Ion FormedName of Cation Sodium1Na + Sodium Calcium2Ca 2+ Calcium Magnesium 2Mg 2+ Magnesium What is the rule for naming cations? DON’T CHANGE THE NAME. 6

7 Anions  Negatively charged ions  Nonmetal atom gains electrons  Name changes to –ide ending Example: Name of Element: Iodine Number of Valence Electrons: 7 Charge on Ion: -1 Name of Ion: Iodide 7

8 Naming Anions Practice Element# of Valence ElectronsIon FormedName of Anion Nitrogen5N 3- Nitride Sulfur6S 2- Sulfide Fluorine7F-F- Fluoride What is the rule for naming anions? CHANGE THE ENDING TO -IDE 8

9 Note: Groups 14 (4A) and 18 (8A) usually do not form ions 9

10 10

11 Ions of Transition Metals  Many of the transition metals form more than one cation with different ionic charges  Not all transition metals have more than one charge  Charges must be determined from the number of electrons lost These colorful solutions contain the transition metal ions Co 3+, Cr 3+, Fe 3+, Ni 2+, and Mn

12 Two Methods to Name Transition Metal Ions 1. Stock System 2. Classical Method 12

13 Stock System  Preferred method of naming  A Roman numeral in parentheses is placed after the name of the element to indicate the numerical value of the charge NumberRoman Numeral 1I 2II 3III 4IV 5V 6VI 13

14 Stock System Naming Practice Ion Formed# Electrons LostStock Name Cu + 1Copper (I) ion Cu 2+ 2Copper (II) ion Pb 2+ 2Lead (II) ion Pb 4+ 4Lead (IV) ion 14

15 Classical Method  In the past, scientists used the Latin names of elements. Example: Ferrum is Latin for Iron. Ferr- is the root of this word. Iron forms two ions: Fe 2+ and Fe 3+ Ion names: Fe 2+ is the ferrous ion Fe 3+ is the ferric ion 15

16 16

17 Practice Problems a) Selenide (anion) b) Barium (cation) c) Phosphide (anion) 17

18 Polyatomic Ions  What does the prefix poly mean?  MANY  Polyatomic ions are composed of more than one atom  Tightly bound groups of atoms that behave as a unit and carry a charge  The names of most polyatomic ions end in –ite or –ate  Different Endings Ammonium  NH 4 + Cyanide  CN - Hydroxide  OH - 18

19 19

20 Polyatomic Ions to memorize! 20 FormulaName NO 3 - Nitrate OH - Hydroxide ClO 3 - Chlorate SO 4 2- Sulfate CO 3 2- Carbonate PO 4 3- Phosphate

21 A closer look at a polyatomic ion PO 4 3- Name: Phosphate Subscript: shows the number of atoms of that element Superscript: shows the charge on the polyatomic ion What is the subscript on Phosphorus? 1 21

22 An important note:  Pay close attention to the names!  Example:  Sulfide = S 2-  Sulfate = SO 4 2-  Sulfite = SO

23 Section 9.1 Quick Quiz

24 1. Which of the following are positively charged polyatomic ions? (I) ammonium ion (II) perchlorate ion (III) iron (II) ion a. I only b. II only c. III only d. I and III 24

25 2. If the name of an ion ends in -ite or -ate, the ion is a a. polyatomic cation. b. polyatomic anion. c. transition metal cation. d. monatomic anion. 25

26 Read pages Section 9.2: Naming and Writing Formulas for Ionic Compounds

27 Different Types of Ionic Compounds 1. Simple Ionic Compounds (last chapter!) 2. Ionic Compounds Involving Transition Metals 1. Transition metals with only 1 charge 2. Transition metals with more than 1 possible charge 3. Ionic Compounds Involving Polyatomic Ions 27

28 Binary Ionic Compounds  What does the prefix bi mean?  TWO  A binary ionic compound is composed of two elements - a metal and a nonmetal 28

29 Naming Binary Ionic Compounds  If you know the formula of the ionic compound, you can write the name  To name any binary ionic compound, place the cation name first, followed by the anion name. 29

30 Naming Simple Ionic Compounds (last chapter) CaCl 2 What is the name of the cation? What is the name of the anion? CalciumChloride 1 Metal + 1 Nonmetal 30

31 Naming Simple Ionic Compounds (last chapter) Li 2 O What is the name of the cation? What is the name of the anion? LithiumOxide 1 Metal + 1 Nonmetal 31

32 Naming Ionic Compounds Containing a Transition Metal with ONE possible charge ZnS What is the name of the cation? What is the name of the anion? ZincSulfide WAIT! What’s special about the cation? Zinc is a transition metal. It has 1 possible charge. We don’t need a Roman numeral because there is only 1 possible charge! 1 Transition Metal + 1 Nonmetal 32

33 Cu 2 O What is the name of the cation? What is the name of the anion? Copper (I) Oxide What’s special about the cation? Copper is a transition metal. It has two possible charges (+1 or +2). Don’t forget the roman numeral!!! (based on oxygen’s charge) What is the charge on an oxygen ion? 2- Naming Ionic Compounds Containing a Transition Metal with more than one possible charge 1 Transition Metal + 1 Nonmetal 33

34 CuO What is the name of the cation? What is the name of the anion? Copper (II)Oxide Naming Ionic Compounds Containing a Transition Metal with more than one possible charge 1 Transition Metal + 1 Nonmetal 34

35 Try It!  Name the following binary ionic compounds: 1. NaF 2. FeCl 3 3. FeCl 2 1. Sodium Fluoride 2. Iron (III) Chloride 3. Iron (II) Chloride 35

36 Writing Binary Ionic Formulas  If you know the name of a binary ionic compound, you can write the formula!  Write the symbol of the cation and then the anion. Then, add the subscripts that are needed to balance the charges.  The positive charge of the cation must balance the negative charge of the anion so that the net ionic charge of the compound is neutral. 36

37 Remember the crisscross method? 1.Determine the charge on each ion. 2.Cross the charges. 3.Reduce if necessary. 4.Name the compound. 37

38 Simple Ionic Compounds Formulas  Write the formula for Sodium Bromide. First: What is the cation? Second: What is the anion? Na + - Br NaBr 38

39 Ionic Compounds with Transition Metals  Write the formula for Iron (III) Oxide. First: What is the cation? Second: What is the anion? Fe O Fe 2 O 3 39

40 CuS K3NK3N NaI CaI 2 K2SK2S 40

41 What is a polyatomic ion? 41  Tightly bound groups of atoms that behave as a unit and carry a charge

42 Polyatomic Ions behave as a UNIT. 42  You CANNOT change the charge or the number of atoms of each element in a polyatomic ion or you will change the identity of that ion!!  ClO – Hypochlorite  ClO 2 – Chlorite  ClO 3 – Chlorate  ClO 4 – Perchlorate

43 Naming Compounds with Polyatomic Ions  To name a compound containing a polyatomic ion, state the cation first, and then the anion.  Just like naming binary ionic compounds!  Except you DO NOT change the anion name! 43

44 Naming Compounds with Polyatomic Ions Example CaSO 4 What is the name of the cation? What is the name of the anion? CalciumSulfate What’s special about the anion? SO 4 is a polyatomic ion. 44

45 Naming Compounds with Polyatomic Ions Example AlPO 4 What is the name of the cation? What is the name of the anion? AluminumPhosphate 45

46 Naming Compounds with Polyatomic Ions Example NaCH 3 COO What is the name of the cation? What is the name of the anion? SodiumAcetate 46

47 Be aware – you can’t forget about your transition metals! CuSiO 3 What is the name of the cation? What is the name of the anion? Copper (II)Silicate 47

48 Writing the Formula of a Compound Containing a Polyatomic Ion  Remember: Polyatomic ions behave as a unit.  You cannot change the assigned subscript.  Write the symbol for the cation, followed by the formula for the polyatomic ion, then balance the charges. Use parentheses. 48

49 Writing Formulas w/ Polyatomic Ions Example  Write the formula for Aluminum Chromate. Al CrO 4 Al 2 (CrO 4 ) 3 49

50 Writing Formulas w/ Polyatomic Ions Example  Write the formula for Ammonium Sulfide. NH S (NH 4 ) 2 S 50

51 Writing Formulas w/ Polyatomic Ions Example  Write the formula for Ammonium Sulfate. NH SO 4 (NH 4 ) 2 SO 4 51

52 Remember – there can still be compounds with transition metals!  Write the formula for Tin (II) Cyanide. Sn 2+ - CN Sn(CN) 2 52

53 a.Mg(OH) 2 b.K 2 SO 4 53

54 54 That is a representative metal or transition metal with only 1 charge Ionic That is a transition metal with multiple possible charges Bonded to a polyatomic ion Name cation (name stays same) Name anion (ending in –ide) Name cation (use roman numerals) Name anion (ending in –ide) Name cation (see above) Name anion (polyatomic name)

55 Try It!  Write the formulas of the following binary ionic compounds: 1. Tin (IV) sulfide 2. Magnesium nitrate 3. Calcium bromide 4. Sodium hydroxide 1. SnS 2 2. Mg(NO 3 ) 2 3. CaBr 2 4. NaOH 55

56 Section 9.2 Quick Quiz

57 1. The correct name for CrCl 3 is a. chromium chlorine. b. chromium(III) chloride. c. monochromium trichloride. d. chromium(III) trichloride. 57

58 2. What is the correct formula for strontium nitride? a. Sr 3 N 2 b. SrN 2 c. Sr 2 N 3 d. Sr 3 N 58

59 3. Which one of the following compounds is named correctly? a. sodium chlorite, NaClO b. potassium nitrate, KNO 3 c. sodium acetate, Na 2 C 2 H 3 O 2 d. lithium sulfate, Li 2 SO 3 59

60 What’s Next?  Book Work  Page 258 (#8-9)  Page 266 (#17-19) 60

61 Page 258 #8 and 9 Page 266 # Write the symbol for the ion of each element. Classify the ion as an anion or cation, and name the ion. a.Potassium b.Oxygen c.Tin (2 electrons lost) d.Bromine e.Beryllium f.Cobalt (3 electrons lost) 9.Write the symbol or formula (including charge) for each of the following ions. a.Ammonium ion b.Tin (II) ion c.Chromate ion d.Nitrate ion 17.Write the formulas of the following compounds: a.Beryllium Chloride b.Cesium Sulfide c.Sodium Iodide d.Strontium Oxide 18. Write the formulas of these polyatomic compounds: a.Chromium (III) nitrate b.Sodium perchlorate c.Magnesium hydrogen carbonate d.Calcium acetate 19. Identify any incorrect formulas and explain your reasoning. a.Mg 2 (SO 4 ) 3 b.Rb 3 As c.BeCl 3 d.NaF 61

62 #8 – Write the symbol for the ion of each element. Classify the ion as an anion or cation, and name the ion. a. Potassium  K +, cation, Potassium b. Oxygen  O 2-, anion, Oxide a. Tin (2 electrons lost)  Sn 2+, cation, Tin (II) b. Bromine  Br -, anion, Bromide c. Beryllium  Be 2+, cation, Beryllium d. Cobalt (3 electrons lost)  Co 3+, cation, Cobalt (III) 62

63 #9 – Write the symbol or formula (including charge) for each of the following ions. a. Ammonium ion  NH 4 + b. Tin (II) ion  Sn 2+ c. Chromate ion  CrO 4 2- d. Nitrate ion  NO

64 #17 – Write the formula for these binary compounds. a. Beryllium Chloride b. Cesium Sulfide c. Sodium Iodide d. Strontium Oxide a. BeCl 2 b. Cs 2 S c. NaI d. SrO 64

65 #18 – Write the formula these compounds containing polyatomic ions. a. Chromium (III) nitrate b. Sodium Perchlorate c. Magnesium hydrogen carbonate d. Calcium acetate a. Cr(NO 3 ) 3 b. NaClO 4 c. Mg(HCO 3 ) 2 d. Ca(C 2 H 3 O 2 ) 2 or Ca(CH 3 COO) 2 65

66 #19 – Identify any incorrect formulas. Explain your answer. a. Mg 2 (SO 4 ) 3 b. Rb 3 As c. BeCl 3 d. NaF 66

67 Read pages Section 9.3: Naming and Writing Formulas for Molecular Compounds

68 Binary Molecular Compounds  A binary molecular compound is composed of two elements – both are nonmetals  Binary molecular compounds do not contain ions – they are made of… molecules 68

69 Carbon and oxygen combine to form carbon monoxide (CO) and carbon dioxide (CO 2 ), but these two invisible gases are very different. Sitting in a room with small amounts of CO 2 in the air would not present any problems. If the same amount of CO were in the room, you could die of asphyxiation. A naming system that distinguishes between these two compounds is needed. 69

70 Naming Binary Molecular Compounds  Use prefixes  The prefix in the name of a binary molecular compound tells how many atoms of each element are present in each molecule of the compound 70

71 Steps for Naming a Binary Molecular Compound 1. Confirm that the compound is a binary molecular compound. 2. Name the elements in the order that they appear in the formula a. Use prefixes to indicate the number of each kind of atom. b. The name of the first element stays the same. The ending of the second element changes to –ide. 71

72 Quick Example – Add it to your notes! S 2 Br 4 sulfurbromide di tetra 72

73 Special Rules  If there is only one atom of the first element in the formula, drop the mono-  If the element begins with a vowel, drop the vowel on the end of the prefix. CCl 4 is called carbon tetrachloride, NOT monocarbon tetrachloride. CO is called carbon monoxide, NOT carbon monooxide. 73 Exceptions: Di- and Tri-

74 Naming Binary Molecular Compounds Example 1 N2ON2O nitrogen oxidedi mon 74

75 Naming Binary Molecular Compounds Example 2 Cl 2 O 8 chlorineoxidedioct 75

76 Try It!  Write the names of the following binary molecular compounds: 1. CBr 4 2. N 2 H 4 3. PCl 5 4. S 2 F Carbon tetrabromide 2. Dinitrogen tetrahydride 3. Phosphorus pentachloride 4. Disulfur decafluoride 76

77 Writing Formulas for Binary Molecular Compounds  Use the prefixes in the name to tell you the subscript of each element in the formula. Then, write the correct symbols for the two elements with the appropriate subscripts. 77

78 Writing Formulas for Binary Molecular Compounds Example 1 Dinitrogen trioxide NO 23 78

79 Writing Formulas for Binary Molecular Compounds Example 2 Iodine heptafluoride I F 7 79

80 Try it! a. Carbon disulfide b. Tribromine octoxide c. Silicon monocarbide d. Dihydrogen monoxide a. CS 2 b. Br 3 O 8 c. SiC d. H 2 O 80

81 81 That is a representative metal or transition metal with only 1 charge Ionic That is a transition metal with multiple possible charges Bonded to a polyatomic ion Name cation (name stays same) Name anion (ending in –ide) Name cation (use roman numerals) Name anion (ending in –ide) Name cation (see above) Name anion (polyatomic name) Name compound using prefixes Second element ends in -ide Covalent

82 Section 9.3 Quick Quiz

83 1. Which of the following compounds is named INCORRECTLY? a. CS 2, carbon disulfide b. BCl 3, boron trichloride c. IF 7, iodine heptafluoride d. PCl 5, phosphorus hexachloride 83

84 2. Which of the following molecular compounds is named INCORRECTLY? a. SbCl 3, antimony trichloride b. C 2 O 5, dicarbon pentoxide c. CF 4, carbon tetrafluoride d. H 3 S, hydrogen sulfide 84

85 3. The correct formula for tetraphosphorus trisulfide is a. P 3 S 4 b. S 3 P 4 c. P 4 S 3 d. S 4 P 3 85

86 Read pages Section 9.4: Naming and Writing Formulas for Acids and Bases

87 Naming Acids  Acid - a compound that contains one or more hydrogen atoms and produces hydrogen ions (H + ) when dissolved in water  Hydrogen is most commonly listed first in the compound  Formula: H n X NOTE: Acids do not have to have hydrogen first, but usually do. 87

88 Rules for Naming Acids 88  Three rules  Dependent on the anion (the non hydrogen part)

89 Rule #1 89  When the name of the anion ends in –ide, the acid name begins with hydro-. The stem of the anion has the suffix –ic and is followed by acid.  Simply – if there is no oxygen in the acid formula, the formula for the name is hydro-root-ic acid.  Example  HCl Cation – Hydrogen Anion – Chloride Name of Acid – Hydrochloric Acid

90 Rule #2 90  When the anion name ends in –ite, the acid name is the stem of the anion with the suffix –ous followed by the word acid.  Formula for name: Root-ous acid  Example  HClO 2 Cation – Hydrogen Anion – Chlorite Name of Acid – Chlorous acid

91 Rule #3 91  When the anion name ends in –ate, the acid name is the stem of the anion with the suffix –ic followed by the word acid.  Formula for name: Root-ic acid  Example  HClO 3 Cation – Hydrogen Anion – Chlorate Name of Acid – Chloric acid

92 Weird Roots 92  Sulfur and Phosphorus  Sulfur  Sulfuric, Sulfurous  Phosphorus  Phosphoric, Phosphorous

93 Practice Problems 93  Name the following acids: 1. H 2 SO 3 1. Sulfurous Acid 2. HNO 3 1. Nitric Acid 3. HBr 1. Hydrobromic Acid 4. H 3 PO 3 1. Phosphorous Acid PO 3 3- is phosphite

94 Writing Formulas for Acids 94  Use the rules in reverse  Example:  Write the formula for hydrocyanic acid.  Hydro-root-ic acid means the anion ends in –ide. The cation is Hydrogen (H + ). The anion is Cyanide (CN - ). The formula for the acid is HCN.

95 Practice Problems 95  Write the formulas for the following acids: 1. Hydroiodic acid 1. HI 2. Carbonic acid 1. H 2 CO 3 3. Carbonous acid 1. H 2 CO 2 4. Acetic acid HC 2 H 3 O 2 CO 2 2- is carbonite

96 Names and Formulas of Bases 96  Base – a compound that produces hydroxide ions (OH - ) when dissolved in water  Named the same way as an ionic compound: Name of cation, then name of anion.  Anion is usually hydroxide (OH-) but it does not have to be.  Example:  NaOH Cation: Sodium Anion: Hydroxide Name of Base: Sodium Hydroxide

97 Try it! 97  Provide the appropriate name or formula of the following bases: 1. Potassium hydroxide 1. KOH 2. Be(OH) 2 1. Beryllium Hydroxide 3. RbOH 1. Rubidium Hydroxide 4. Aluminum hydroxide 1. Al(OH) 3

98 A base to take note of: 98  NH 3 is ammonia.  This is an example of a base that does NOT contain a hydroxide ion.

99 Weird Roots 99  Sulfur and Phosphorus  Sulfur  Sulfuric, Sulfurous  Phosphorus  Phosphoric, Phosphorous

100 100 That is a representative metal or transition metal with only 1 charge Ionic That is a transition metal with multiple possible charges Bonded to a polyatomic ion Name cation (name stays same) Name anion (ending in –ide) Name cation (use roman numerals) Name anion (ending in –ide) Name cation (see above) Name anion (polyatomic name) If the anion is hydroxide (OH - ) then you have a base Name compound using prefixes (second element ends in –ide) Does not contain any oxygen (Anion ends in –ide) Hydro(root)ic acid Anion ends in -ite (Root)ous acid Anion ends in -ate (Root)ic acid Acid Covalent

101 Molecular Naming Review CO 2 2. CO 3. P 2 O 5 4. N 2 O 5. SO 2 6. CBr 4 7. SO 2 8. PBr 5 9. ICl NI N 2 O 3 1. Dinitrogen tetroxide 2. Sulfur trioxide 3. Nitrogen monoxide 4. Nitrogen dioxide 5. Diarsenic pentoxide 6. Phosphorus trichloride 7. Carbon tetrachloride 8. Dihydrogen monoxide 9. Selenium hexafluoride

102 Acid/Base Naming Review HF 11. H 2 S 12. H 2 CO LiOH 14. HNO Co(OH) H 2 SO Be(OH) HBr 1. Sodium hydroxide 2. Sulfurous acid 3. Hydrosulfuric acid 4. Phosphoric acid 5. Ammonia 6. Hydrocyanic acid 7. Calcium hydroxide 8. Iron (III) hydroxide 9. Hydrophosphoric acid

103 Section 9.4 Quick Quiz

104 1. An acid is a compound that produces WHAT when dissolved in water? a. Hydroxide ions b. Hydrogen ions c. Polyatomic ions d. Molecules 104

105 2. Which of the following formulas is correct for the base: Calcium Hydroxide a. CaOH 2 b. CaH c. CaOH d. Ca(OH) 2 105

106 What’s Next?  Practice Problems 106

107 22.Write the names of the following compounds: a.NCl 3 b.BCl 3 c.Nl 3 23.Write the formulas or names of the following compounds: a.CS 2 b.Carbon tetrabromide c.Cl 2 O 7 d.Diphosphorus trioxide 24.Write the molecular formulas of the following compounds: a.Phosphorus pentachloride b.Iodine heptafluoride c.Chlorine trifluoride d.Iodine dioxide 25.The name a student gives for themolecular compound SiCl 4 is monosilicon trichloride. Is this name correct? Explain. 107 d.SO 3 e.N 2 H 4 f.N 2 O 3 29.Name the following acids: 29.HNO 2 30.HMnO 4 31.HCN 32.H 2 S 30.Name the following bases: 29.LiOH 30.Pb(OH) 2 31.Mg(OH) 2 32.Al(OH) 3 31.Write formulas for each of the following acids and bases: 29.Carbonic acid 30.Sulfurous acid 31.Iron (III) hydroxide 32.Strontium hydroxide

108 #22 – Write the names for these molecular compounds. a. Nitrogen trichloride b. Boron trichloride c. Nitrogen triodide d. Sulfur trioxide e. Dinitrogen tetrahydride f. Dinitrogen trioxide a. NCl 3 b. BCl 3 c. Nl 3 d. SO 3 e. N 2 H 4 f. N 2 O 3 108

109 #23 – Write the formulas or names for these molecular compounds. a. CS 2 b. Carbon tetrabromide c. Cl 2 O 7 d. Diphosphorus trioxide a. Carbon disulfide b. CBr 4 c. Dichlorine heptoxide d. P 2 O 3 109

110 #24 – Write the formulas for these binary molecular compounds. a. Phosphorus pentachloride b. Iodine heptafluoride c. Chlorine trifluoride d. Iodine dioxide a. PCl 5 b. IF 7 c. ClF 3 d. IO 2 110

111 #25 – The name a student gives for the molecular compound SiCl 4 is monosilicon trichloride. Is this name correct? Explain.  Silicon tetrachloride 111

112 #29 – Give the names of these acids. A. HNO 2 B. HMnO 4 C. HCN D. H 2 S A. Nitrous acid B. Permanganic acid C. Hydrocyanic acid D. Hydrosulfuric acid 112

113 #30 – Write the names of these bases. A. LiOH B. Pb(OH) 2 C. Mg(OH) 2 D. Al(OH) 3 A. Lithium hydroxide B. Lead (II) hydroxide C. Magnesium hydroxide D. Aluminum hydroxide 113

114 #32 – Write the formulas of the following acids and bases: A. Carbonic acid B. Sulfurous acid C. Iron (III) hydroxide D. Strontium hydroxide A. H 2 CO 3 B. H 2 SO 3 C. Fe(OH) 3 D. Sr(OH) 2 114

115 Read pages Section 9.5: The Laws Governing Formulas and Names

116 The Laws Governing Formulas and Names  The rules for naming and writing formulas are possible because elements form compounds in predictable ways.  Two Important Laws  The Law of Definite Proportions  The Law of Multiple Proportions 116

117 The Law of Definite Proportions  States that in samples of any chemical compound, the masses of the elements are always in the same proportions.  So what does that mean? 117

118 Law of Definite Proportions Continued  Water  What is the formula for water? H 2 O  What is the atomic mass of Oxygen?  What is the atomic mass of Hydrogen? 1.00  What is the mass ratio of Oxygen to Hydrogen in water? 16:2 which reduces to 8:1  Hydrogen Peroxide  Dihydrogen Dioxide  What is the formula for hydrogen peroxide?  H 2 O 2  What is the mass ratio of Oxygen to Hydrogen in water? 32:2 which reduces to 16:1 Regardless of how much you have, the ratio of masses is always the same! 118

119 Both water and hydrogen peroxide are composed of hydrogen and oxygen…. But they have different properties. 119

120 Law of Multiple Proportions  Whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers. Two Compounds (X and Y) contain equal masses of Element B. The ratio of the masses of Element A in these compounds is 5:10 or 1:2. 120

121 Main Idea: 121  In any chemical compound, the elements are always in the same proportion by MASS.

122 Guidelines for Writing the Chemical Formula of a Compound 1. An –ide ending generally indicates a binary compound. 2. An –ite or –ate ending means a polyatomic ion that contains oxygen is in the formula. 3. Prefixes in a name generally indicate that the compound is molecular. 4. A Roman numeral after the name of a cation shows the charge of the cation. 122

123 Naming Review 1. H in front of the formula? It’s an acid! 2. OH in the formula? It’s a base! (Ionic name) 3. Metal present? It’s ionic! 1. Check to see if you have a transition metal with multiple charges. 4. Only nonmetals? It’s covalent! 123

124 Naming Practice FormulaNameIonic or Molecular? Sodium chloride BrF 3 LiNO 3 Dinitrogen tetrahydride Potassium hydroxide Rb 2 O Hydrofluoric acid 124

125 Naming Practice Answers FormulaNameIonic or Molecular? NaClSodium chlorideIonic BrF 3 Bromine trifluorideMolecular LiNO 3 Lithium nitrateIonic N2H4N2H4 Dinitrogen tetrahydrideMolecular KOHPotassium hydroxideIonic Rb 2 O Rubidium oxideIonic HF Hydrofluoric acidIonic 125

126 What’s Next?  Book Work  Page 279 (#35, 39-41) 126

127 #35 – What two laws describe how chemical compounds form?  The Law of Definite Proportions  The Law of Multiple Proportions 127

128 #39 – Name these compounds: a. Calcium carbonate b. Lead (II) chromate c. Tin (II) dichromate a. CaCO 3 b. PbCrO 4 c. SnCr 2 O 7 128

129 #40 – Write the formulas for these compounds: a. Tin (II) hydroxide b. Barium Fluoride Sn(OH) 2 BaF 2 129

130 #40 – Identify the incorrect names or formulas. a. Calcium (II) oxide b. Aluminum oxide c. Na 2 C 2 O 4 d. Mg(NH 4 ) 2 130


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