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The document discusses the concepts of constant composition of pure substances and the molecular basis for this observation. It specifically addresses: - Pure substances have a constant ratio of elements regardless of sample size due to their molecular makeup. - Compounds are made of molecules with specific numbers and types of atoms, so every sample contains identical molecules. - The document provides examples of using formulas to represent compounds and determining the number of atoms present. It also discusses classifying different types of elements and compounds.

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Law of Constant Composition All pure substances have constant composition. All samples of a pure substance contain the same elements in the same percentages (ratios). Mixtures have variable composition. Tro's "Introductory Chemistry", Chapter 5
Compounds Display Constant Composition If we decompose 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. Tro's "Introductory Chemistry", Chapter 5
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. Tro's "Introductory Chemistry", Chapter 5
Formulas Describe Compounds, Continued Tro's "Introductory Chemistry", Chapter 5 Water = H 2 O  two atoms of hydrogen and 1 atom of oxygen Table sugar = C 12 H 22 O 11  12 atoms of C, 22 atoms of H and 11 atoms O
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 . Tro's "Introductory Chemistry", Chapter 5 Table 5.1 Order of Listing Nonmetals in Chemical Formulas C P N H S I Br Cl O F
Practice—Write Formulas for Each of the Following Compounds. Hematite—Composed of four oxide ions for every three iron ions. Acetone—Each molecule contains six hydrogen atoms, three carbon atoms, and one oxygen atom. Tro's "Introductory Chemistry", Chapter 5 Fe 3 O 4 C 3 H 6 O
Molecules with Polyatomic Ions Tro's "Introductory Chemistry", Chapter 5 Mg( NO 3 ) 2 Compound called magnesium nitrate. Ca SO 4 Compound called calcium sulfate. Symbol of the polyatomic ion called nitrate . Symbol of the polyatomic ion called sulfate . Implied “1” subscript on magnesium. Implied “1” subscript on calcium. Parentheses to group two NO 3 s. No parentheses for one SO 4 .
Molecules with Polyatomic Ions, Continued Mg( NO 3 ) 2 Compound called magnesium nitrate. Ca SO 4 Compound called calcium sulfate. Subscript indicating two NO 3 groups. No subscript indicating one SO 4 group. Implied “1” subscript on nitrogen, total 2 N. Implied “1” subscript on sulfur, total 1 S. Stated “3” subscript on oxygen, total 6 O. Stated “4” subscript on oxygen, total 4 O.
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 (Hg 2 ) 3 (PO 4 ) 2 Tro's "Introductory Chemistry", Chapter 5 1 Mg + 4 C + 6 H + 4 O = 15 6 Hg + 2 P + 8 O = 16
Classifying Materials Atomic elements = Elements whose particles are single atoms. Molecular elements = Elements whose particles are multi-atom molecules. Molecular compounds = Compounds whose particles are molecules made of only nonmetals. Ionic compounds = Compounds whose particles are cations and anions. Tro's "Introductory Chemistry", Chapter 5
Molecular Elements Certain elements occur as diatomic molecules. 7 diatomic elements—The Rule of 7s Find the element with atomic number 7, N. Make a figure 7 by going over to Group 7A, then down. The seventh element is H 2 . H 2 Cl 2 Br 2 I 2 7 7A N 2 O 2 F 2
Molecular Compounds Two or more nonmetals. Smallest unit is a molecule. Tro's "Introductory Chemistry", Chapter 5
Ionic Compounds Metals + nonmetals. No individual molecule units, instead have a 3-dimensional array of cations and anions made of formula units . Tro's "Introductory Chemistry", Chapter 5
Molecular View of Elements and Compounds
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. Tro's "Introductory Chemistry", Chapter 5
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. Tro's "Introductory Chemistry", Chapter 5
Ionic Compounds Ionic compounds are made of ions. Ionic compounds always contain cations and anions. Cations = + charged ions; anions = − charged ions. The sum of the + charges of the cations must equal the sum of the − charges of the anions. If Na + is combined with S 2- , you will need 2 Na + ions for every S 2- ion to balance the charges, therefore the formula must be Na 2 S. Tro's "Introductory Chemistry", Chapter 5
Writing Formulas for Ionic Compounds Write the symbol for the metal cation and its charge. Write the symbol for the nonmetal anion and its charge. Charge (without sign) becomes subscript for the other ion. Reduce subscripts to smallest whole-number ratio. Check that the sum of the charges of the cation cancels the sum of the anions. Tro's "Introductory Chemistry", Chapter 5
Write the Formula of a Compound Made from Aluminum Ions and Oxide Ions. Write the symbol for the metal cation and its charge. Write the symbol for the nonmetal anion and its charge. Charge (without sign) becomes subscript for the other ion. Reduce subscripts to smallest whole-number ratio. Check that the total charge of the cations cancels the total charge of the anions. Tro's "Introductory Chemistry", Chapter 5 Al +3 column 3A O 2- column 6A Al +3 O 2- Al 2 O 3 Al = (2)∙(+3) = +6 O = (3)∙(-2) = -6
Practice—What Are the Formulas for Compounds Made from the Following Ions? Potassium ion with a nitride ion. Calcium ion with a bromide ion. Aluminum ion with a sulfide ion. Tro's "Introductory Chemistry", Chapter 5
Practice—What Are the Formulas for Compounds Made from the Following Ions?, Continued K + with N 3- K 3 N Ca +2 with Br - CaBr 2 Al +3 with S 2- Al 2 S 3 Tro's "Introductory Chemistry", Chapter 5
Formula-to-Name Step 1 Is the compound one of the exceptions to the rules? Tro's "Introductory Chemistry", Chapter 5
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. Tro's "Introductory Chemistry", Chapter 5
Formula-to-Name Step 2 What major class of compound is it? Ionic or Molecular? Tro's "Introductory Chemistry", Chapter 5
Major Classes Ionic compounds. Metal + nonmetal(s). Metal first in formula. Binary ionic or compounds with polyatomic ions. Molecular compounds. 2 or more nonmetals. Binary molecular (or binary covalent). 2 nonmetals. Acids— Formula starts with H. Though acids are molecular, they behave as ionic when dissolved in water. May be binary or oxyacid. Tro's "Introductory Chemistry", Chapter 5
Formula-to-Name Step 3 What major subclass of compound is it? Binary Ionic, Ionic with Polyatomic Ions, Binary Molecular, Binary Acid, or Oxyacid? Tro's "Introductory Chemistry", Chapter 5
Classifying Compounds Compounds containing a metal and a nonmetal = Binary ionic. Type I and II. Compounds containing a polyatomic ion = Ionic with polyatomic ion. Compounds containing two nonmetals = Binary molecular compounds. Compounds containing H and a nonmetal = Binary acids. Compounds containing H and a polyatomic ion = Oxyacids. Tro's "Introductory Chemistry", Chapter 5
Formula-to-Name Step 4 Apply rules for the class and subclass. Tro's "Introductory Chemistry", Chapter 5
Formula-to-Name Rules for Ionic Made of cation and anion. Name by simply naming the ions. If cation is: Type I metal = Metal name. Type II metal = Metal name (charge). Polyatomic ion = Name of polyatomic ion. If anion is: Nonmetal = Stem of nonmetal name + - ide . Polyatomic ion = Name of polyatomic ion. Tro's "Introductory Chemistry", Chapter 5
Monatomic Nonmetal Anion Determine the charge from position on the periodic table. To name anion, change ending on the element name to – ide . Tro's "Introductory Chemistry", Chapter 5 4A = -4 5A = -3 6A = -2 7A = -1 C = Carbide N = Nitride O = Oxide F = Fluoride Si = Silicide P = Phosphide S = Sulfide Cl = Chloride
Metal Cations Type I Metals whose ions can only have one possible charge. 1A, 2A, (Al, Zn, Ag). Determine charge by position on the periodic table. 1A = +, 2A = 2+, Al = 3+. Some need to be memorized. Zn = 2+, Ag = +. Type II Metals whose ions can have more than one possible charge. Determine charge by charge on anion. Tro's "Introductory Chemistry", Chapter 5 How do you know a metal cation is Type II?
Determine if the Following Metals are Type I or Type II. If Type I, Determine the Charge on the Cation it Forms. Lithium, Li. Copper, Cu. Gallium, Ga. Tin, Sn. Strontium, Sr. Tro's "Introductory Chemistry", Chapter 5
Determine if the Following Metals are Type I or Type II. If Type I, Determine the Charge on the Cation it Forms, Continued. Lithium, Li Type I 1+ Copper, Cu Type II Gallium, Ga Type I 3+ Tin, Sn Type II Strontium, Sr Type I 2+ Tro's "Introductory Chemistry", Chapter 5
Type I Binary Ionic Compounds Contain metal cation + nonmetal anion. Metal listed first in formula and name. Name metal cation first, name nonmetal anion second. Cation name is the metal name. Nonmetal anion named by changing the ending on the nonmetal name to –ide. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Binary Ionic, Type I Metal, CsF Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. Cs is a metal because it is on the left side of the periodic table. F is a nonmetal because it is on the right side of the periodic table.  Ionic. Identify the subclass. 2 elements,  Binary ionic. Is the metal Type I or Type II? Cs is in Group 1A,  Type I. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Binary Ionic, Type I Metal, CsF, Continued Identify cation and anion. Cs = Cs + because it is Group 1A. F = F - because it is Group 7A. Name the cation. Cs + = cesium. Name the anion. F - = fluoride. Write the cation name first, then the anion name. cesium fluoride. Tro's "Introductory Chemistry", Chapter 5
Practice—Name the Following Compounds. KCl MgBr 2 Al 2 S 3 Tro's "Introductory Chemistry", Chapter 5
Practice—Name the Following Compounds, Continued. KCl potassium chloride . MgBr 2 magnesium bromide . Al 2 S 3 aluminum sulfide . Tro's "Introductory Chemistry", Chapter 5
Type II Binary Ionic Compounds Contain metal cation + nonmetal anion. Metal listed first in formula and name. Name metal cation first, name nonmetal anion second. Metal cation name is the metal name followed by a roman numeral in parentheses to indicate its charge. Determine charge from anion charge. Common Type II cations in Table 5.5. Nonmetal anion named by changing the ending on the nonmetal name to –ide . Tro's "Introductory Chemistry", Chapter 5
Determining the Charge on a Variable Charge Cation—Au 2 S 3 Determine the charge on the anion. Au 2 S 3 - the anion is S, since it is in Group 6A, its charge is 2 −. Determine the total negative charge. S ince there are 3 S in the formula, the total negative charge is − 6. Determine the total positive charge. S ince the total negative charge is − 6, the total positive charge is +6. Divide by the number of cations. S ince there are 2 Au in the formula and the total positive charge is +6, each Au has a 3+ charge. Tro's "Introductory Chemistry", Chapter 5
Example—Writing Formula for a Binary Ionic Compound Containing Variable Charge Metal, Manganese(IV) Sulfide Write the symbol for the cation and its charge. Write the symbol for the anion and its charge. Charge (without sign) becomes subscript for the other ion. Reduce subscripts to smallest whole-number ratio. Check that the total charge of the cations cancels the total charge of the anions. Tro's "Introductory Chemistry", Chapter 5 Mn +4 S 2- Mn +4 S 2- Mn 2 S 4 Mn = (1)∙(+4) = +4 S = (2)∙(-2) = -4 MnS 2
Practice—What Are the Formulas for Compounds Made from the Following Ions? Copper(II) ion with a nitride ion. Iron(III) ion with a bromide ion. Tro's "Introductory Chemistry", Chapter 5
Practice—What Are the Formulas for Compounds Made from the Following Ions?, Continued Cu 2+ with N 3- Cu 3 N 2 Fe +3 with Br - FeBr 3 Tro's "Introductory Chemistry", Chapter 5
Example—Naming Binary Ionic, Type II Metal, CuCl Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. Cu is a metal because it is on the left side of the periodic table. Cl is a nonmetal because it is on the right side of the periodic table.  Ionic. Identify the subclass. 2 elements,  Binary ionic. Is the metal Type I or Type II? Cu is not in Group 1A, 2A, or (Al, Zn, Ag)  Type II. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Binary Ionic, Type II Metal, CuCl, Continued Identify cation and anion. Cl = Cl − because it is Group 7A. Cu = Cu + to balance the charge. Name the cation. Cu + = Copper(I). Name the anion. Cl − = Chloride. Write the cation name first, then the anion name. Copper(I) chloride. Tro's "Introductory Chemistry", Chapter 5
Practice ─ Name the Following Compounds. TiCl 4 PbBr 2 Fe 2 S 3 Tro's "Introductory Chemistry", Chapter 5
Practice ─ Name the Following Compounds, Continued. TiCl 4 Titanium(IV) chloride . PbBr 2 Lead(II) bromide . Fe 2 S 3 Iron(III) sulfide . Tro's "Introductory Chemistry", Chapter 5 Cl = 4( − 1) = −4 Ti = +4 = 1(4+) Br = 2( − 1) = −2 Pb = +2 = 1(2+) S = 3( − 2) = −6 Pb = +6 = 2(3+)
Compounds Containing Polyatomic Ions Polyatomic ions are single ions that contain more than one atom. Name any ionic compound by naming cation first and then anion. Non-polyatomic cations named like Type I and II. Non-polyatomic anions named with – ide . Tro's "Introductory Chemistry", Chapter 5
Some Common Polyatomic Ions Name Formula Acetate C 2 H 3 O 2 – Carbonate CO 3 2 – Hydrogencarbonate (aka bicarbonate) HCO 3 – Hydroxide OH – Nitrate NO 3 – Nitrite NO 2 – Chromate CrO 4 2 – Dichromate Cr 2 O 7 2 – Ammonium NH 4 + Name Formula Hypochlorite ClO – Chlorite ClO 2 – Chlorate ClO 3 – Perchlorate ClO 4 – Sulfate SO 4 2 – Sulfite SO 3 2 – Hydrogen sulfate (aka bisulfate) HSO 4 – Hydrogen sulfite (aka bisulfite) HSO 3 –
Example—Writing Formula for an Ionic Compound Containing Polyatomic Ion, Iron(III) phosphate Write the symbol for the cation and its charge. Write the symbol for the anion and its charge. Charge (without sign) becomes subscript for the other ion. Reduce subscripts to smallest whole-number ratio. Check that the total charge of the cations cancels the total charge of the anions. Tro's "Introductory Chemistry", Chapter 5 Fe +3 PO 4 3- Fe +3 PO 4 3- Fe 3 (PO 4 ) 3 Fe = (1)∙(+3) = +3 PO 4 = (1)∙(-3) = -3 FePO 4
Practice—What Are the Formulas for Compounds Made from the Following Ions? Aluminum ion with a sulfate ion. Chromium(II) with hydrogencarbonate. Tro's "Introductory Chemistry", Chapter 5
Practice—What Are the Formulas for Compounds Made from the Following Ions?, Continued Al +3 with SO 4 2- Al 2 (SO 4 ) 3 Cr +2 with HCO 3 ─ Cr(HCO 3 ) 2 Tro's "Introductory Chemistry", Chapter 5
Patterns for Polyatomic Ions Elements in the same column form similar polyatomic ions. Same number of Os and same charge. ClO 3 - = chlorate  BrO 3 - = bromate. If the polyatomic ion starts with H, the name adds hydrogen - prefix before it and 1is added to the charge. CO 3 2- = carbonate  HCO 3 -1 = hydrogencarbonate. Tro's "Introductory Chemistry", Chapter 5
Periodic Pattern of Polyatomic Ions -ate Groups Tro's "Introductory Chemistry", Chapter 5 3A 4A 5A 6A 7A BO 3 -3 NO 3 -1 SiO 3 -2 PO 4 -3 SO 4 -2 ClO 3 -1 AsO 4 -3 SeO 4 -2 BrO 3 -1 TeO 4 -2 IO 3 -1 CO 3 -2
Patterns for Polyatomic Ions -ate ion. Chlorate = ClO 3 -1 . -ate ion + 1 O  same charge, per- prefix. Perchlorate = ClO 4 -1 . -ate ion – 1 O  same charge, - ite suffix. Chlorite = ClO 2 -1 . -ate ion – 2 O  same charge, hypo- prefix, - ite suffix. Hypochlorite = ClO -1 . Tro's "Introductory Chemistry", Chapter 5
Example—Naming Ionic with Polyatomic Ion, Na 2 SO 4 Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. Na is a metal because it is on the left side of the periodic table. SO 4 is a polyatomic ion.  Ionic Identify the subclass. Compound has 3 elements  Ionic with polyatomic ion. Is the metal Type I or Type II? Na is in Group 1A,  Type I. Tro's "Introductory Chemistry", Chapter 5
Identify the ions. Na = Na + because in Group 1A. SO 4 = SO 4 2- a polyatomic ion. Name the cation. Na + = sodium (Type I). Name the anion. SO 4 2- = sulfate. Write the name of the cation followed by the name of the anion. sodium sulfate. Example—Naming Ionic with Polyatomic Ion, Na 2 SO 4 , Continued Tro's "Introductory Chemistry", Chapter 5
Example—Naming Ionic with Polyatomic Ion, Fe(NO 3 ) 3 Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. Fe is a metal because it is on the left side of the periodic table. NO 3 is a polyatomic ion because it is in ( ).  Ionic. Identify the subclass. There are 3 elements  Ionic with polyatomic ion. Is the metal Type I or Type II? Cu is not in Group 1A, 2A, or (Al, Zn, Ag)  Type II. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Ionic with Polyatomic Ion, Fe(NO 3 ) 3 , Continued Identify the ions. NO 3 = NO 3 − a polyatomic ion. Fe = Fe 3+ to balance the charge of the 3 NO 3 − . Name the cation. Fe 3+ = iron(III) (Type II). Name the anion. NO 3 − = nitrate. Write the name of the cation followed by the name of the anion. iron(III) nitrate.
Practice─Name the Following NH 4 Cl Ca(C 2 H 3 O 2 ) 2 Cu(NO 3 ) 2 Tro's "Introductory Chemistry", Chapter 5
Practice─Name the Following, Continued NH 4 Cl Ammonium chloride. Ca(C 2 H 3 O 2 ) 2 Calcium acetate. Cu(NO 3 ) 2 Copper(II) nitrate. Tro's "Introductory Chemistry", Chapter 5 NO 3 = 2( − 1) = −2 Cu = +2 = 1(2+)
Formula-to-Name Rules for Molecular We will not learn the rules for molecular compounds with more than 2 elements. For binary molecular: Name first nonmetal. Then name second nonmetal with - ide ending. Then give each name a prefix to indicate its subscript in the formula. Tro's "Introductory Chemistry", Chapter 5
Binary Molecular Compounds of Two Nonmetals Name first element in formula first. Use the full name of the element. Name the second element in the formula with an − ide, as if it were an anion. However, remember these compounds do not contain ions! Use a prefix in front of each name to indicate the number of atoms. Never use the prefix mono- on the first element.
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. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Binary Molecular, BF 3 Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. B is a nonmetal because it is on the right side of the periodic table. F is a nonmetal because it is on the right side of the periodic table.  Molecular. Identify the subclass. 2 elements,  Binary molecular. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Binary Molecular, BF 3 , Continued Name the first element. boron. Name the second element with an –ide. Fluorine  fluoride. Add a prefix to each name to indicate the subscript. monoboron, trifluoride. Write the first element with prefix, then the second element with prefix. Drop prefix mono- from first element. boron trifluoride.
Formula-to-Name Acids Acids are molecular compounds that often behave like they are made of ions. All names have acid at end. Binary Acids = Hydro- prefix + stem of the name of the nonmetal + -ic suffix. Oxyacids: If polyatomic ion ends in –ate = Name of polyatomic ion with –ic suffix. If polyatomic ion ends in – ite = Name of polyatomic ion with –ous suffix. Tro's "Introductory Chemistry", Chapter 5
Practice─Name the Following NO 2 PCl 5 I 2 F 7 Tro's "Introductory Chemistry", Chapter 5
Practice─Name the Following Continued NO 2 Nitrogen dioxide. PCl 5 Phosphorus pentachloride. I 2 F 7 Diiodine heptafluoride. Tro's "Introductory Chemistry", Chapter 5
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. Tro's "Introductory Chemistry", Chapter 5
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. Tro's "Introductory Chemistry", Chapter 5
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. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Binary Acids, HCl Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. First element listed is H,  Acid. Identify the subclass. 2 elements,  Binary acid. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Binary Acids, HCl, Continued Identify the anion. Cl = Cl − , chloride because Group 7A. Name the anion with an – ic suffix. Cl − = chloride  chloric Add a hydro- prefix to the anion name. hydrochloric Add the word acid to the end. hydrochloric acid Tro's "Introductory Chemistry", Chapter 5
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. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Oxyacids, H 2 SO 4 Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. First element listed is H,  Acid. Identify the subclass. 3 elements in the formula,  Oxyacid. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Oxyacids, H 2 SO 4 ,Continued Identify the anion. SO 4 = SO 4 2- = sulfate. If the anion has – ate suffix, change it to – ic . If the anion has – ite suffix, change it to – ous. SO 4 2- = sulfate  sulfuric . Write the name of the anion followed by the word acid. sulfuric acid (This is kind of an exception, to make it sound nicer!) Tro's "Introductory Chemistry", Chapter 5
Example—Naming Oxyacids, H 2 SO 3 Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. First element listed is H,  Acid. Identify the subclass. 3 elements in the formula,  Oxyacid. Tro's "Introductory Chemistry", Chapter 5
Example—Naming Oxyacids, H 2 SO 3 , Continued Identify the anion. SO 3 = SO 3 2- = sulfite If the anion has – ate suffix, change it to – ic . If the anion has – ite suffix, change it to – ous. SO 3 2- = sulfite  sulfurous Write the name of the anion followed by the word acid. sulfurous acid Tro's "Introductory Chemistry", Chapter 5
Practice─Name the Following H 2 S HClO 3 HNO 2 Tro's "Introductory Chemistry", Chapter 5
Practice─Name the Following Continued H 2 S hydrosulfuric acid . HClO 3 chloric acid . HNO 2 nitrous acid . Tro's "Introductory Chemistry", Chapter 5
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 –ous . Tro's "Introductory Chemistry", Chapter 5
Example—Binary Acids, Hydrosulfuric Acid Write the symbol for the cation and its charge. Write the symbol for the anion and its charge. Charge (without sign) becomes subscript for the other ion. Add ( aq ) to indicate dissolved in water. Check that the total charge of the cations cancels the total charge of the anions. Tro's "Introductory Chemistry", Chapter 5 H + S 2- H + S 2- H 2 S H = (2)∙(+1) = +2 S = (1)∙(-2) = -2 H 2 S ( aq ) In all acids, the cation is H + . Hydro- means binary.
Example—Oxyacids, Carbonic Acid Write the symbol for the cation and its charge. Write the symbol for the anion and its charge. Charge (without sign) becomes subscript for the other ion. Add ( aq ) to indicate dissolved in water. Check that the total charge of the cations cancels the total charge of the anions. Tro's "Introductory Chemistry", Chapter 5 H + CO 3 2- H + CO 3 2- H 2 CO 3 H = (2)∙(+1) = +2 CO 3 = (1)∙(-2) = -2 H 2 CO 3 ( aq ) In all acids, the cation is H + . No hydro- means polyatomic ion. -ic means - ate ion.
Example—Oxyacids, Sulfurous Acid Write the symbol for the cation and its charge. Write the symbol for the anion and its charge. Charge (without sign) becomes subscript for the other ion. Add ( aq ) to indicate dissolved in water. Check that the total charge of the cations cancels the total charge of the anions . Tro's "Introductory Chemistry", Chapter 5 H + SO 3 2- H + SO 3 2- H 2 SO 3 H = (2)∙(+1) = +2 SO 3 = (1)∙(-2) = -2 H 2 SO 3 ( aq ) In all acids, the cation is H + . No hydro- means polyatomic ion. -ous means - ite ion.
Practice—What Are the Formulas for the Following Acids? Chlorous acid Phosphoric acid Hydrobromic acid Tro's "Introductory Chemistry", Chapter 5
Practice—What Are the Formulas for the Following Acids?, Continued H + with ClO 2 – HClO 2 H + with PO 4 3 – H 3 PO 4 H + with Br – HBr Tro's "Introductory Chemistry", Chapter 5
Formula-to-Name Flowchart Tro's "Introductory Chemistry", Chapter 5
Formula Mass The mass of an individual molecule or formula unit. Also known as molecular mass or molecular weight. Sum of the masses of the atoms in a single molecule or formula unit. Whole = Sum of the parts. Mass of 1 molecule of H 2 O = 2(1.01 amu H) + 16.00 amu O = 18.02 amu. Tro's "Introductory Chemistry", Chapter 5
Practice—Calculate the Formula Mass of Al 2 (SO 4 ) 3 . Tro's "Introductory Chemistry", Chapter 5
Practice—Calculate the Formula Mass of Al 2 (SO 4 ) 3 , Continued. Tro's "Introductory Chemistry", Chapter 5

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Tro3 lecture 05

  • 1. Law of Constant Composition All pure substances have constant composition. All samples of a pure substance contain the same elements in the same percentages (ratios). Mixtures have variable composition. Tro's "Introductory Chemistry", Chapter 5
  • 2. Compounds Display Constant Composition If we decompose 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. Tro's "Introductory Chemistry", Chapter 5
  • 3. 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. Tro's "Introductory Chemistry", Chapter 5
  • 4. Formulas Describe Compounds, Continued Tro's "Introductory Chemistry", Chapter 5 Water = H 2 O  two atoms of hydrogen and 1 atom of oxygen Table sugar = C 12 H 22 O 11  12 atoms of C, 22 atoms of H and 11 atoms O
  • 5. 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 . Tro's "Introductory Chemistry", Chapter 5 Table 5.1 Order of Listing Nonmetals in Chemical Formulas C P N H S I Br Cl O F
  • 6. Practice—Write Formulas for Each of the Following Compounds. Hematite—Composed of four oxide ions for every three iron ions. Acetone—Each molecule contains six hydrogen atoms, three carbon atoms, and one oxygen atom. Tro's "Introductory Chemistry", Chapter 5 Fe 3 O 4 C 3 H 6 O
  • 7. Molecules with Polyatomic Ions Tro's "Introductory Chemistry", Chapter 5 Mg( NO 3 ) 2 Compound called magnesium nitrate. Ca SO 4 Compound called calcium sulfate. Symbol of the polyatomic ion called nitrate . Symbol of the polyatomic ion called sulfate . Implied “1” subscript on magnesium. Implied “1” subscript on calcium. Parentheses to group two NO 3 s. No parentheses for one SO 4 .
  • 8. Molecules with Polyatomic Ions, Continued Mg( NO 3 ) 2 Compound called magnesium nitrate. Ca SO 4 Compound called calcium sulfate. Subscript indicating two NO 3 groups. No subscript indicating one SO 4 group. Implied “1” subscript on nitrogen, total 2 N. Implied “1” subscript on sulfur, total 1 S. Stated “3” subscript on oxygen, total 6 O. Stated “4” subscript on oxygen, total 4 O.
  • 9. 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 (Hg 2 ) 3 (PO 4 ) 2 Tro's "Introductory Chemistry", Chapter 5 1 Mg + 4 C + 6 H + 4 O = 15 6 Hg + 2 P + 8 O = 16
  • 10. Classifying Materials Atomic elements = Elements whose particles are single atoms. Molecular elements = Elements whose particles are multi-atom molecules. Molecular compounds = Compounds whose particles are molecules made of only nonmetals. Ionic compounds = Compounds whose particles are cations and anions. Tro's "Introductory Chemistry", Chapter 5
  • 11. Molecular Elements Certain elements occur as diatomic molecules. 7 diatomic elements—The Rule of 7s Find the element with atomic number 7, N. Make a figure 7 by going over to Group 7A, then down. The seventh element is H 2 . H 2 Cl 2 Br 2 I 2 7 7A N 2 O 2 F 2
  • 12. Molecular Compounds Two or more nonmetals. Smallest unit is a molecule. Tro's "Introductory Chemistry", Chapter 5
  • 13. Ionic Compounds Metals + nonmetals. No individual molecule units, instead have a 3-dimensional array of cations and anions made of formula units . Tro's "Introductory Chemistry", Chapter 5
  • 14. Molecular View of Elements and Compounds
  • 15. 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. Tro's "Introductory Chemistry", Chapter 5
  • 16. 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. Tro's "Introductory Chemistry", Chapter 5
  • 17. Ionic Compounds Ionic compounds are made of ions. Ionic compounds always contain cations and anions. Cations = + charged ions; anions = − charged ions. The sum of the + charges of the cations must equal the sum of the − charges of the anions. If Na + is combined with S 2- , you will need 2 Na + ions for every S 2- ion to balance the charges, therefore the formula must be Na 2 S. Tro's "Introductory Chemistry", Chapter 5
  • 18. Writing Formulas for Ionic Compounds Write the symbol for the metal cation and its charge. Write the symbol for the nonmetal anion and its charge. Charge (without sign) becomes subscript for the other ion. Reduce subscripts to smallest whole-number ratio. Check that the sum of the charges of the cation cancels the sum of the anions. Tro's "Introductory Chemistry", Chapter 5
  • 19. Write the Formula of a Compound Made from Aluminum Ions and Oxide Ions. Write the symbol for the metal cation and its charge. Write the symbol for the nonmetal anion and its charge. Charge (without sign) becomes subscript for the other ion. Reduce subscripts to smallest whole-number ratio. Check that the total charge of the cations cancels the total charge of the anions. Tro's "Introductory Chemistry", Chapter 5 Al +3 column 3A O 2- column 6A Al +3 O 2- Al 2 O 3 Al = (2)∙(+3) = +6 O = (3)∙(-2) = -6
  • 20. Practice—What Are the Formulas for Compounds Made from the Following Ions? Potassium ion with a nitride ion. Calcium ion with a bromide ion. Aluminum ion with a sulfide ion. Tro's "Introductory Chemistry", Chapter 5
  • 21. Practice—What Are the Formulas for Compounds Made from the Following Ions?, Continued K + with N 3- K 3 N Ca +2 with Br - CaBr 2 Al +3 with S 2- Al 2 S 3 Tro's "Introductory Chemistry", Chapter 5
  • 22. Formula-to-Name Step 1 Is the compound one of the exceptions to the rules? Tro's "Introductory Chemistry", Chapter 5
  • 23. 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. Tro's "Introductory Chemistry", Chapter 5
  • 24. Formula-to-Name Step 2 What major class of compound is it? Ionic or Molecular? Tro's "Introductory Chemistry", Chapter 5
  • 25. Major Classes Ionic compounds. Metal + nonmetal(s). Metal first in formula. Binary ionic or compounds with polyatomic ions. Molecular compounds. 2 or more nonmetals. Binary molecular (or binary covalent). 2 nonmetals. Acids— Formula starts with H. Though acids are molecular, they behave as ionic when dissolved in water. May be binary or oxyacid. Tro's "Introductory Chemistry", Chapter 5
  • 26. Formula-to-Name Step 3 What major subclass of compound is it? Binary Ionic, Ionic with Polyatomic Ions, Binary Molecular, Binary Acid, or Oxyacid? Tro's "Introductory Chemistry", Chapter 5
  • 27. Classifying Compounds Compounds containing a metal and a nonmetal = Binary ionic. Type I and II. Compounds containing a polyatomic ion = Ionic with polyatomic ion. Compounds containing two nonmetals = Binary molecular compounds. Compounds containing H and a nonmetal = Binary acids. Compounds containing H and a polyatomic ion = Oxyacids. Tro's "Introductory Chemistry", Chapter 5
  • 28. Formula-to-Name Step 4 Apply rules for the class and subclass. Tro's "Introductory Chemistry", Chapter 5
  • 29. Formula-to-Name Rules for Ionic Made of cation and anion. Name by simply naming the ions. If cation is: Type I metal = Metal name. Type II metal = Metal name (charge). Polyatomic ion = Name of polyatomic ion. If anion is: Nonmetal = Stem of nonmetal name + - ide . Polyatomic ion = Name of polyatomic ion. Tro's "Introductory Chemistry", Chapter 5
  • 30. Monatomic Nonmetal Anion Determine the charge from position on the periodic table. To name anion, change ending on the element name to – ide . Tro's "Introductory Chemistry", Chapter 5 4A = -4 5A = -3 6A = -2 7A = -1 C = Carbide N = Nitride O = Oxide F = Fluoride Si = Silicide P = Phosphide S = Sulfide Cl = Chloride
  • 31. Metal Cations Type I Metals whose ions can only have one possible charge. 1A, 2A, (Al, Zn, Ag). Determine charge by position on the periodic table. 1A = +, 2A = 2+, Al = 3+. Some need to be memorized. Zn = 2+, Ag = +. Type II Metals whose ions can have more than one possible charge. Determine charge by charge on anion. Tro's "Introductory Chemistry", Chapter 5 How do you know a metal cation is Type II?
  • 32. Determine if the Following Metals are Type I or Type II. If Type I, Determine the Charge on the Cation it Forms. Lithium, Li. Copper, Cu. Gallium, Ga. Tin, Sn. Strontium, Sr. Tro's "Introductory Chemistry", Chapter 5
  • 33. Determine if the Following Metals are Type I or Type II. If Type I, Determine the Charge on the Cation it Forms, Continued. Lithium, Li Type I 1+ Copper, Cu Type II Gallium, Ga Type I 3+ Tin, Sn Type II Strontium, Sr Type I 2+ Tro's "Introductory Chemistry", Chapter 5
  • 34. Type I Binary Ionic Compounds Contain metal cation + nonmetal anion. Metal listed first in formula and name. Name metal cation first, name nonmetal anion second. Cation name is the metal name. Nonmetal anion named by changing the ending on the nonmetal name to –ide. Tro's "Introductory Chemistry", Chapter 5
  • 35. Example—Naming Binary Ionic, Type I Metal, CsF Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. Cs is a metal because it is on the left side of the periodic table. F is a nonmetal because it is on the right side of the periodic table.  Ionic. Identify the subclass. 2 elements,  Binary ionic. Is the metal Type I or Type II? Cs is in Group 1A,  Type I. Tro's "Introductory Chemistry", Chapter 5
  • 36. Example—Naming Binary Ionic, Type I Metal, CsF, Continued Identify cation and anion. Cs = Cs + because it is Group 1A. F = F - because it is Group 7A. Name the cation. Cs + = cesium. Name the anion. F - = fluoride. Write the cation name first, then the anion name. cesium fluoride. Tro's "Introductory Chemistry", Chapter 5
  • 37. Practice—Name the Following Compounds. KCl MgBr 2 Al 2 S 3 Tro's "Introductory Chemistry", Chapter 5
  • 38. Practice—Name the Following Compounds, Continued. KCl potassium chloride . MgBr 2 magnesium bromide . Al 2 S 3 aluminum sulfide . Tro's "Introductory Chemistry", Chapter 5
  • 39. Type II Binary Ionic Compounds Contain metal cation + nonmetal anion. Metal listed first in formula and name. Name metal cation first, name nonmetal anion second. Metal cation name is the metal name followed by a roman numeral in parentheses to indicate its charge. Determine charge from anion charge. Common Type II cations in Table 5.5. Nonmetal anion named by changing the ending on the nonmetal name to –ide . Tro's "Introductory Chemistry", Chapter 5
  • 40. Determining the Charge on a Variable Charge Cation—Au 2 S 3 Determine the charge on the anion. Au 2 S 3 - the anion is S, since it is in Group 6A, its charge is 2 −. Determine the total negative charge. S ince there are 3 S in the formula, the total negative charge is − 6. Determine the total positive charge. S ince the total negative charge is − 6, the total positive charge is +6. Divide by the number of cations. S ince there are 2 Au in the formula and the total positive charge is +6, each Au has a 3+ charge. Tro's "Introductory Chemistry", Chapter 5
  • 41. Example—Writing Formula for a Binary Ionic Compound Containing Variable Charge Metal, Manganese(IV) Sulfide Write the symbol for the cation and its charge. Write the symbol for the anion and its charge. Charge (without sign) becomes subscript for the other ion. Reduce subscripts to smallest whole-number ratio. Check that the total charge of the cations cancels the total charge of the anions. Tro's "Introductory Chemistry", Chapter 5 Mn +4 S 2- Mn +4 S 2- Mn 2 S 4 Mn = (1)∙(+4) = +4 S = (2)∙(-2) = -4 MnS 2
  • 42. Practice—What Are the Formulas for Compounds Made from the Following Ions? Copper(II) ion with a nitride ion. Iron(III) ion with a bromide ion. Tro's "Introductory Chemistry", Chapter 5
  • 43. Practice—What Are the Formulas for Compounds Made from the Following Ions?, Continued Cu 2+ with N 3- Cu 3 N 2 Fe +3 with Br - FeBr 3 Tro's "Introductory Chemistry", Chapter 5
  • 44. Example—Naming Binary Ionic, Type II Metal, CuCl Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. Cu is a metal because it is on the left side of the periodic table. Cl is a nonmetal because it is on the right side of the periodic table.  Ionic. Identify the subclass. 2 elements,  Binary ionic. Is the metal Type I or Type II? Cu is not in Group 1A, 2A, or (Al, Zn, Ag)  Type II. Tro's "Introductory Chemistry", Chapter 5
  • 45. Example—Naming Binary Ionic, Type II Metal, CuCl, Continued Identify cation and anion. Cl = Cl − because it is Group 7A. Cu = Cu + to balance the charge. Name the cation. Cu + = Copper(I). Name the anion. Cl − = Chloride. Write the cation name first, then the anion name. Copper(I) chloride. Tro's "Introductory Chemistry", Chapter 5
  • 46. Practice ─ Name the Following Compounds. TiCl 4 PbBr 2 Fe 2 S 3 Tro's "Introductory Chemistry", Chapter 5
  • 47. Practice ─ Name the Following Compounds, Continued. TiCl 4 Titanium(IV) chloride . PbBr 2 Lead(II) bromide . Fe 2 S 3 Iron(III) sulfide . Tro's "Introductory Chemistry", Chapter 5 Cl = 4( − 1) = −4 Ti = +4 = 1(4+) Br = 2( − 1) = −2 Pb = +2 = 1(2+) S = 3( − 2) = −6 Pb = +6 = 2(3+)
  • 48. Compounds Containing Polyatomic Ions Polyatomic ions are single ions that contain more than one atom. Name any ionic compound by naming cation first and then anion. Non-polyatomic cations named like Type I and II. Non-polyatomic anions named with – ide . Tro's "Introductory Chemistry", Chapter 5
  • 49. Some Common Polyatomic Ions Name Formula Acetate C 2 H 3 O 2 – Carbonate CO 3 2 – Hydrogencarbonate (aka bicarbonate) HCO 3 – Hydroxide OH – Nitrate NO 3 – Nitrite NO 2 – Chromate CrO 4 2 – Dichromate Cr 2 O 7 2 – Ammonium NH 4 + Name Formula Hypochlorite ClO – Chlorite ClO 2 – Chlorate ClO 3 – Perchlorate ClO 4 – Sulfate SO 4 2 – Sulfite SO 3 2 – Hydrogen sulfate (aka bisulfate) HSO 4 – Hydrogen sulfite (aka bisulfite) HSO 3 –
  • 50. Example—Writing Formula for an Ionic Compound Containing Polyatomic Ion, Iron(III) phosphate Write the symbol for the cation and its charge. Write the symbol for the anion and its charge. Charge (without sign) becomes subscript for the other ion. Reduce subscripts to smallest whole-number ratio. Check that the total charge of the cations cancels the total charge of the anions. Tro's "Introductory Chemistry", Chapter 5 Fe +3 PO 4 3- Fe +3 PO 4 3- Fe 3 (PO 4 ) 3 Fe = (1)∙(+3) = +3 PO 4 = (1)∙(-3) = -3 FePO 4
  • 51. Practice—What Are the Formulas for Compounds Made from the Following Ions? Aluminum ion with a sulfate ion. Chromium(II) with hydrogencarbonate. Tro's "Introductory Chemistry", Chapter 5
  • 52. Practice—What Are the Formulas for Compounds Made from the Following Ions?, Continued Al +3 with SO 4 2- Al 2 (SO 4 ) 3 Cr +2 with HCO 3 ─ Cr(HCO 3 ) 2 Tro's "Introductory Chemistry", Chapter 5
  • 53. Patterns for Polyatomic Ions Elements in the same column form similar polyatomic ions. Same number of Os and same charge. ClO 3 - = chlorate  BrO 3 - = bromate. If the polyatomic ion starts with H, the name adds hydrogen - prefix before it and 1is added to the charge. CO 3 2- = carbonate  HCO 3 -1 = hydrogencarbonate. Tro's "Introductory Chemistry", Chapter 5
  • 54. Periodic Pattern of Polyatomic Ions -ate Groups Tro's "Introductory Chemistry", Chapter 5 3A 4A 5A 6A 7A BO 3 -3 NO 3 -1 SiO 3 -2 PO 4 -3 SO 4 -2 ClO 3 -1 AsO 4 -3 SeO 4 -2 BrO 3 -1 TeO 4 -2 IO 3 -1 CO 3 -2
  • 55. Patterns for Polyatomic Ions -ate ion. Chlorate = ClO 3 -1 . -ate ion + 1 O  same charge, per- prefix. Perchlorate = ClO 4 -1 . -ate ion – 1 O  same charge, - ite suffix. Chlorite = ClO 2 -1 . -ate ion – 2 O  same charge, hypo- prefix, - ite suffix. Hypochlorite = ClO -1 . Tro's "Introductory Chemistry", Chapter 5
  • 56. Example—Naming Ionic with Polyatomic Ion, Na 2 SO 4 Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. Na is a metal because it is on the left side of the periodic table. SO 4 is a polyatomic ion.  Ionic Identify the subclass. Compound has 3 elements  Ionic with polyatomic ion. Is the metal Type I or Type II? Na is in Group 1A,  Type I. Tro's "Introductory Chemistry", Chapter 5
  • 57. Identify the ions. Na = Na + because in Group 1A. SO 4 = SO 4 2- a polyatomic ion. Name the cation. Na + = sodium (Type I). Name the anion. SO 4 2- = sulfate. Write the name of the cation followed by the name of the anion. sodium sulfate. Example—Naming Ionic with Polyatomic Ion, Na 2 SO 4 , Continued Tro's "Introductory Chemistry", Chapter 5
  • 58. Example—Naming Ionic with Polyatomic Ion, Fe(NO 3 ) 3 Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. Fe is a metal because it is on the left side of the periodic table. NO 3 is a polyatomic ion because it is in ( ).  Ionic. Identify the subclass. There are 3 elements  Ionic with polyatomic ion. Is the metal Type I or Type II? Cu is not in Group 1A, 2A, or (Al, Zn, Ag)  Type II. Tro's "Introductory Chemistry", Chapter 5
  • 59. Example—Naming Ionic with Polyatomic Ion, Fe(NO 3 ) 3 , Continued Identify the ions. NO 3 = NO 3 − a polyatomic ion. Fe = Fe 3+ to balance the charge of the 3 NO 3 − . Name the cation. Fe 3+ = iron(III) (Type II). Name the anion. NO 3 − = nitrate. Write the name of the cation followed by the name of the anion. iron(III) nitrate.
  • 60. Practice─Name the Following NH 4 Cl Ca(C 2 H 3 O 2 ) 2 Cu(NO 3 ) 2 Tro's "Introductory Chemistry", Chapter 5
  • 61. Practice─Name the Following, Continued NH 4 Cl Ammonium chloride. Ca(C 2 H 3 O 2 ) 2 Calcium acetate. Cu(NO 3 ) 2 Copper(II) nitrate. Tro's "Introductory Chemistry", Chapter 5 NO 3 = 2( − 1) = −2 Cu = +2 = 1(2+)
  • 62. Formula-to-Name Rules for Molecular We will not learn the rules for molecular compounds with more than 2 elements. For binary molecular: Name first nonmetal. Then name second nonmetal with - ide ending. Then give each name a prefix to indicate its subscript in the formula. Tro's "Introductory Chemistry", Chapter 5
  • 63. Binary Molecular Compounds of Two Nonmetals Name first element in formula first. Use the full name of the element. Name the second element in the formula with an − ide, as if it were an anion. However, remember these compounds do not contain ions! Use a prefix in front of each name to indicate the number of atoms. Never use the prefix mono- on the first element.
  • 64. 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. Tro's "Introductory Chemistry", Chapter 5
  • 65. Example—Naming Binary Molecular, BF 3 Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. B is a nonmetal because it is on the right side of the periodic table. F is a nonmetal because it is on the right side of the periodic table.  Molecular. Identify the subclass. 2 elements,  Binary molecular. Tro's "Introductory Chemistry", Chapter 5
  • 66. Example—Naming Binary Molecular, BF 3 , Continued Name the first element. boron. Name the second element with an –ide. Fluorine  fluoride. Add a prefix to each name to indicate the subscript. monoboron, trifluoride. Write the first element with prefix, then the second element with prefix. Drop prefix mono- from first element. boron trifluoride.
  • 67. Formula-to-Name Acids Acids are molecular compounds that often behave like they are made of ions. All names have acid at end. Binary Acids = Hydro- prefix + stem of the name of the nonmetal + -ic suffix. Oxyacids: If polyatomic ion ends in –ate = Name of polyatomic ion with –ic suffix. If polyatomic ion ends in – ite = Name of polyatomic ion with –ous suffix. Tro's "Introductory Chemistry", Chapter 5
  • 68. Practice─Name the Following NO 2 PCl 5 I 2 F 7 Tro's "Introductory Chemistry", Chapter 5
  • 69. Practice─Name the Following Continued NO 2 Nitrogen dioxide. PCl 5 Phosphorus pentachloride. I 2 F 7 Diiodine heptafluoride. Tro's "Introductory Chemistry", Chapter 5
  • 70. 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. Tro's "Introductory Chemistry", Chapter 5
  • 71. 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. Tro's "Introductory Chemistry", Chapter 5
  • 72. 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. Tro's "Introductory Chemistry", Chapter 5
  • 73. Example—Naming Binary Acids, HCl Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. First element listed is H,  Acid. Identify the subclass. 2 elements,  Binary acid. Tro's "Introductory Chemistry", Chapter 5
  • 74. Example—Naming Binary Acids, HCl, Continued Identify the anion. Cl = Cl − , chloride because Group 7A. Name the anion with an – ic suffix. Cl − = chloride  chloric Add a hydro- prefix to the anion name. hydrochloric Add the word acid to the end. hydrochloric acid Tro's "Introductory Chemistry", Chapter 5
  • 75. 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. Tro's "Introductory Chemistry", Chapter 5
  • 76. Example—Naming Oxyacids, H 2 SO 4 Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. First element listed is H,  Acid. Identify the subclass. 3 elements in the formula,  Oxyacid. Tro's "Introductory Chemistry", Chapter 5
  • 77. Example—Naming Oxyacids, H 2 SO 4 ,Continued Identify the anion. SO 4 = SO 4 2- = sulfate. If the anion has – ate suffix, change it to – ic . If the anion has – ite suffix, change it to – ous. SO 4 2- = sulfate  sulfuric . Write the name of the anion followed by the word acid. sulfuric acid (This is kind of an exception, to make it sound nicer!) Tro's "Introductory Chemistry", Chapter 5
  • 78. Example—Naming Oxyacids, H 2 SO 3 Is it one of the common exceptions? H 2 O, NH 3 , CH 4 , NaCl, C 12 H 22 O 11 = No! Identify major class. First element listed is H,  Acid. Identify the subclass. 3 elements in the formula,  Oxyacid. Tro's "Introductory Chemistry", Chapter 5
  • 79. Example—Naming Oxyacids, H 2 SO 3 , Continued Identify the anion. SO 3 = SO 3 2- = sulfite If the anion has – ate suffix, change it to – ic . If the anion has – ite suffix, change it to – ous. SO 3 2- = sulfite  sulfurous Write the name of the anion followed by the word acid. sulfurous acid Tro's "Introductory Chemistry", Chapter 5
  • 80. Practice─Name the Following H 2 S HClO 3 HNO 2 Tro's "Introductory Chemistry", Chapter 5
  • 81. Practice─Name the Following Continued H 2 S hydrosulfuric acid . HClO 3 chloric acid . HNO 2 nitrous acid . Tro's "Introductory Chemistry", Chapter 5
  • 82. 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 –ous . Tro's "Introductory Chemistry", Chapter 5
  • 83. Example—Binary Acids, Hydrosulfuric Acid Write the symbol for the cation and its charge. Write the symbol for the anion and its charge. Charge (without sign) becomes subscript for the other ion. Add ( aq ) to indicate dissolved in water. Check that the total charge of the cations cancels the total charge of the anions. Tro's "Introductory Chemistry", Chapter 5 H + S 2- H + S 2- H 2 S H = (2)∙(+1) = +2 S = (1)∙(-2) = -2 H 2 S ( aq ) In all acids, the cation is H + . Hydro- means binary.
  • 84. Example—Oxyacids, Carbonic Acid Write the symbol for the cation and its charge. Write the symbol for the anion and its charge. Charge (without sign) becomes subscript for the other ion. Add ( aq ) to indicate dissolved in water. Check that the total charge of the cations cancels the total charge of the anions. Tro's "Introductory Chemistry", Chapter 5 H + CO 3 2- H + CO 3 2- H 2 CO 3 H = (2)∙(+1) = +2 CO 3 = (1)∙(-2) = -2 H 2 CO 3 ( aq ) In all acids, the cation is H + . No hydro- means polyatomic ion. -ic means - ate ion.
  • 85. Example—Oxyacids, Sulfurous Acid Write the symbol for the cation and its charge. Write the symbol for the anion and its charge. Charge (without sign) becomes subscript for the other ion. Add ( aq ) to indicate dissolved in water. Check that the total charge of the cations cancels the total charge of the anions . Tro's "Introductory Chemistry", Chapter 5 H + SO 3 2- H + SO 3 2- H 2 SO 3 H = (2)∙(+1) = +2 SO 3 = (1)∙(-2) = -2 H 2 SO 3 ( aq ) In all acids, the cation is H + . No hydro- means polyatomic ion. -ous means - ite ion.
  • 86. Practice—What Are the Formulas for the Following Acids? Chlorous acid Phosphoric acid Hydrobromic acid Tro's "Introductory Chemistry", Chapter 5
  • 87. Practice—What Are the Formulas for the Following Acids?, Continued H + with ClO 2 – HClO 2 H + with PO 4 3 – H 3 PO 4 H + with Br – HBr Tro's "Introductory Chemistry", Chapter 5
  • 88. Formula-to-Name Flowchart Tro's "Introductory Chemistry", Chapter 5
  • 89. Formula Mass The mass of an individual molecule or formula unit. Also known as molecular mass or molecular weight. Sum of the masses of the atoms in a single molecule or formula unit. Whole = Sum of the parts. Mass of 1 molecule of H 2 O = 2(1.01 amu H) + 16.00 amu O = 18.02 amu. Tro's "Introductory Chemistry", Chapter 5
  • 90. Practice—Calculate the Formula Mass of Al 2 (SO 4 ) 3 . Tro's "Introductory Chemistry", Chapter 5
  • 91. Practice—Calculate the Formula Mass of Al 2 (SO 4 ) 3 , Continued. Tro's "Introductory Chemistry", Chapter 5