Chemical Formulas and Chemical Nomenclature. Mr. Matthew Totaro Legacy High School Honors Chemistry

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1 Chemical Formulas and Chemical Nomenclature Mr. Matthew Totaro Legacy High School Honors Chemistry 1

2 Molecular View of Elements and Compounds 2

3 Atomic Elements Atomic Elements = elements whose smallest units are single atoms Most elements are atomic elements Elemental Mercury 3

4 Molecular Elements Certain elements occur as diatomic molecules. 7 diatomic elements H O F Br I N Cl H 2 7 7A N 2 O 2 F 2 Cl2 Br 2 I 2 4

5 Molecular Compounds Two or more nonmetals. Smallest unit is a molecule. 5

6 Ionic Compounds Metals + nonmetals. No individual molecule units, instead have a 3- dimensional array of cations and anions made of formula units. 6

7 Classify Each of the Following as Either an Atomic Element, Molecular Element, Molecular Compound, or Ionic Compound. Aluminum, Al. Aluminum chloride, AlCl 3. Chlorine, Cl 2. Acetone, C 3 H 6 O. Carbon monoxide, CO. Cobalt, Co. 7

8 Classify Each of the Following as Either an Atomic Element, Molecular Element, Molecular Compound, or Ionic Compound, Continued. Aluminum, Al = Atomic element. Aluminum chloride, AlCl 3 = Ionic compound. Chlorine, Cl 2 = Molecular element. Acetone, C 3 H 6 O = Molecular compound. Carbon monoxide, CO = Molecular compound. Cobalt, Co = Atomic element. 8

9 Law of Constant Composition 9

10 Law of Constant Composition 10

11 Law of Constant Composition All pure substances have constant composition. All samples of a pure substance contain the same elements in the same mass ratios. Mixtures have variable composition. 11

12 Compounds Display Constant Composition If we decompose 18.0 g of water by electrolysis, we find 16.0 grams of oxygen to every 2.00 grams of hydrogen. Water has a constant mass ratio of oxygen to hydrogen of 8.0. Mass Ratio = mass of oxygen mass of hydrogen = 16.0 g 2.0 g =

13 Example Show that Two Samples of Carbon Dioxide, CO 2 Are Consistent with the Law of Constant Composition. Sample 1: 4.8 g O, 1.8 g C; Sample 2: 17.1 g O, 6.4 g C 13

14 Why Do Compounds Show Constant Composition? The smallest piece of a compound is called a molecule. Every molecule of a compound has the same number and type of atoms. Since all the molecules of a compound are identical, every sample will have the same ratio of the elements. Since all molecules of a compound are identical, every sample of the compound will have the same properties. 14

15 Chemical Formulas 15

16 Formulas Describe Compounds A chemical formula describes the compound by describing the number and type of each atom in the simplest unit of the compound. Each element is represented by its letter symbol. The number of atoms of each element is written to the right of the element as a subscript. If there is only one atom, the 1 subscript is not written. C 2 H 2 O 4 16

17 Types of Chemical Formulas 17

18 Formulas Describe Compounds, Continued Water = H 2 O two atoms of hydrogen and 1 atom of oxygen Table sugar = C 12 H 22 O atoms of C, 22 atoms of H and 11 atoms O 18

19 Order of Elements in a Formula Metals are written first. NaCl Nonmetals are written in order from Table 5.1. CO 2 There are occasional exceptions for historical or informational reasons. H 2 O, but NaOH. Table 5.1 Order of Listing Nonmetals in Chemical Formulas C P N H S I Br Cl O F 19

20 Example: Write a formula for ionic compound that forms between calcium and oxygen

21 Example: Write the formula of a compound made from aluminum ions and oxygen ions

22 Practice What are the formulas for compounds made from the following ions? K + with N 3 Ca 2+ with Br Al 3+ with S 2

23 Practice What are the formulas for compounds made from the following ions? K + with N 3 K 3 N Ca 2+ with Br Ca Br 2 Al 3+ with S 2 Al 2 S 3

24 Ion Charge and the Periodic Table The charge on an ion can often be determined from an elements position on the periodic table. Metals are always positive ions, nonmetals are negative ions. For many main group metals, the cation charge = the group number. For nonmetals, the anion charge = the group number 8. 24

25 1A 2A 3A 5A 6A 7A Li + Be 2+ N 3 O 2 F Na + Mg 2+ Al 3+ P 3 S 2 Cl K + Ca 2+ Ga 3+ As 3 Se 2 Br Rb + Sr 2+ In 3+ Te 2 I Cs + Ba 2+

26 Formulas containing Polyatomic Ions 26

27 Compounds Containing Polyatomic Ions Polyatomic ions are single ions that contain more than one atom Often end in ate or -ite Name and charge of polyatomic ion do not change Nitrate Polyatomic Ion (NO 3- )

28 Some Common Polyatomic Ions

29 Polyatomic Ions The polyatomic ions are attracted to opposite ions by ionic bonds. Atoms in the polyatomic ion are held together by covalent bonds. Sodium Cyanide 29

30 Example Write the formula for the ionic compound containing sodium and phosphate

31 Practice What are the formulas for compounds made from the following ions? aluminum ion with a sulfate ion barium ion with hydrogen carbonate ion

32 Molecules with Polyatomic Ions, Continued Subscript indicating two NO 3 groups. No subscript indicating one SO 4 group. Mg(NO 3 ) 2 Compound called magnesium nitrate. Implied 1 subscript on nitrogen, total 2 N. Stated 3 subscript on oxygen, total 6 O. CaSO 4 Compound called calcium sulfate. Implied 1 subscript on sulfur, total 1 S. Stated 4 subscript on oxygen, total 4 O.

33 Practice Determine the Total Number of Atoms or Ions in One Formula Unit of Each of the Following. Mg(C 2 H 3 O 2 ) 2 1 Mg + 4 C + 6 H + 4 O = 15 (Hg 2 ) 3 (PO 4 ) 2 6 Hg + 2 P + 8 O = 16 33

34 Chemical Nomenclature Mg(NO 3 ) 2 Compound called Magnesium Nitrate 34

35 Naming Ions - Cations Metals form cations For each positive charge, the ion has 1 less electron than the neutral atom Na atom = 11 p + and 11 e -, Na + ion = 11 p + and 10 e - Ca atom = 20 p + and 20 e -, Ca 2+ ion = 20 p + and 18 e - Cations are named the same as the metal sodium Na Na + + 1e - sodium ion calcium Ca Ca e - calcium ion 35

36 Naming Ions - Anions Nonmetals form anions For each negative charge, the ion has 1 more electron than the neutral atom F = 9 p + and 9 e -, F = 9 p + and 10 e - O = 8 p + and 8 e -, O 2 = 8 p + and 10 e - Anions are named by changing the ending of the name to -ide fluorine F + 1e - F fluoride ion oxygen O + 2e - O 2 oxide ion 36

37 Binary Nomenclature Type I Metals + a Nonmetal 37

38 Example Naming Binary Ionic, Type I Metal, CsF 38

39 KCl Practice Name the Following Compounds. MgBr 2 Al 2 S 3 39

40 Practice Name the Following Compounds, Continued. KCl potassium chloride. MgBr 2 magnesium bromide. Al 2 S 3 aluminum sulfide. 40

41 Binary Nomenclature Type II Metals + a Nonmetal 41

42 -typically have more than one charge Transition Metal Cations Copper (I) Cu + Silver (I) Ag + Gold (I) Au + mercury (I) Hg 2 +2 zinc Zn +2 copper (II) Cu +2 cadmium (II) Cd +2 mercury (II) Hg +2 tin (II) Sn +2 manganese (II) Mn +2 iron (II) Fe +2 cobalt (II) Co +2 nickel (II) Ni +2 lead (II) Pb +2 chromium (III) Cr +3 gold (III) Au +3 bismuth (III) Bi +3 colbalt (III) Co +3 iron (III) Fe +3 lead (IV) Pb +4 tin (IV) Sn +3

43 Determining the Name of a Type II Compound Au 2 S 3 43

44 Example Naming Binary Ionic, Type II Metal, CuCl 44

45 Practice Name the Following Compounds. TiCl 4 PbBr 2 Fe 2 S 3 45

46 Practice Name the Following Compounds, Continued. TiCl 4 Cl = 4( 1) = 4 Ti = +4 = 1(4+) PbBr 2 Br = 2( 1) = 2 Pb = +2 = 1(2+) Fe 2 S 3 S = 3( 2) = 6 Pb = +6 = 2(3+) Titanium(IV) chloride. Lead(II) bromide. Iron(III) sulfide. 46

47 Example Naming Ionic with Polyatomic Ion, Na 2 SO 4 47

48 Example Naming Ionic with Polyatomic Ion, Fe(NO 3 ) 3 48

49 Practice Name the Following 1. NH 4 Cl 2. Ca(C 2 H 3 O 2 ) 2 3. Cu(NO 3 ) 2 49

50 Practice Name the Following, Continued 1. NH 4 Cl Ammonium chloride. 2. Ca(C 2 H 3 O 2 ) 2 Calcium acetate. 3. Cu(NO 3 ) 2 Copper(II) nitrate. 50

51 Binary Nomenclature Nonmetal (p block)+ a Nonmetal (p block) 51

52 Subscript Prefixes 1 = mono- Not used on first nonmetal. 2 = di- 3 = tri- 4 = tetra- 5 = penta- 6 = hexa- 7 = hepta- 8 = octa- Drop last a if name begins with vowel. 52

53 Example Naming Binary Molecular, BF 3 53

54 Example Naming Binary Molecular, N 2 O 4 54

55 Practice Name the Following NO 2 PCl 5 I 2 F 7 55

56 Practice Name the Following Continued NO 2 Nitrogen dioxide PCl 5 Phosphorus pentachloride I 2 F 7 Diiodine heptafluoride. 56

57 Common Names Exceptions H 2 O = Water, steam, ice. NH 3 = Ammonia. CH 4 = Methane. NaCl = Table salt. C 12 H 22 O 11 = Table sugar. 57

58 Acids Acids are molecular compounds that form H + when dissolved in water. To indicate the compound is dissolved in water, (aq) is written after the formula. Not named as acid if not dissolved in water. Sour taste. Dissolve many metals. Like Zn, Fe, Mg, but not Au, Ag, Pt. Formula generally starts with H. E.g., HCl, H 2 SO 4. 58

59 Acids, Continued Contain H +1 cation and anion. In aqueous solution. Binary acids have H +1 cation and nonmetal anion. Oxyacids have H +1 cation and polyatomic anion. 59

60 Naming Binary Acids Write a hydro- prefix. Follow with the nonmetal name. Change ending on nonmetal name to ic. Write the word acid at the end of the name. 60

61 Example Naming Binary Acids, HCl 61

62 Naming Oxyacids If polyatomic ion name ends in ate, then change ending to ic suffix. If polyatomic ion name ends in ite, then change ending to ous suffix. Write word acid at end of all names. 62

63 Example Naming Oxyacids, H 2 SO 4 63

64 Example Naming Oxyacids, H 2 SO 3 64

65 Practice Name the Following 1. H 2 S 2. HClO 3 3. HNO 2 65

66 Practice Name the Following Continued 1. H 2 S hydrosulfuric acid 2. HClO 3 chloric acid 3. HNO 2 nitrous acid 66

67 Writing Formulas for Acids When name ends in acid, formulas starts with H. Write formulas as if ionic, even though it is molecular. Hydro- prefix means it is binary acid, no prefix means it is an oxyacid. For an oxyacid, if ending is ic, polyatomic ion ends in ate; if ending is ous, polyatomic ion ends in ite. 67

68 Example Binary Acids, Hydrosulfuric Acid 68

69 Example Oxyacids, Carbonic Acid 69

70 Example Oxyacids, Sulfurous Acid 70

71 Practice What Are the Formulas for the Following Acids? 1. Chlorous acid 2. Phosphoric acid 3. Hydrobromic acid 71

72 Practice What Are the Formulas for the Following Acids? 1. Chlorous acid HClO 2 2. Phosphoric acid H 3 PO 4 3. Hydrobromic acid HBr 72

73 Writing Formulas from Names Sodium Sulfate = Na 2 SO 4 73

74 Example -Type I Ionic Compounds Calcium Bromide 74

75 Example Writing Formula for a Binary Ionic Compound Containing Variable Charge Metal, Manganese(IV) Sulfide 75

76 Example Writing Formula for an Ionic Compound Containing Polyatomic Ion, Iron(III) phosphate 76

77 Example -Molecular Compounds Tetraphosphorous Decoxide 77

78 Practice What Are the Formulas for Compounds Made from the Following Ions? 1. Aluminum Sulfide 2. Copper(II) Nitride 3. Iron(III) Bromide 78

79 Practice What Are the Formulas for Compounds Made from the Following Ions? 1. Aluminum Sulfide Al 2 S 3 2. Copper(II) Nitride Cu 3 N 2 3. Iron(III) Bromide FeBr 3 79

80 Practice What Are the Formulas for Compounds Made from the Following Ions? 1. Aluminum Sulfate 2. Chromium(II) Hydrogen Carbonate 3. Diiodine Heptoxide 80

81 Practice What Are the Formulas for Compounds Made from the Following Ions? 1. Aluminum Sulfate Al 2 (SO 4 ) 3 2. Chromium(II) Hydrogen Carbonate Cr(HCO 3 ) 2 3. Diiodine Heptoxide I 2 O 7 81