1. Introductory Chemistry, 2nd Edition Nivaldo Tro
Chapter 5
Molecules and
Compounds
Roy Kennedy
Massachusetts Bay Community College
Wellesley Hills, MA
2006, Prentice Hall

2. Molecules and Compounds
Salt
Sodium – shiny, reactive, poisonous
Chlorine – pale yellow gas, reactive, poisonous
Sodium chloride – table salt
Sugar
Carbon – pencil or diamonds
Hydrogen – flammable gas
Oxygen – a gas in air
Combine to form white crystalline sugar
Tro's Introductory Chemistry, Chapter 5

3. 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

4. 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

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

6. Formulas Describe Compounds
a compound is a distinct substance that is composed of atoms of two or more elements
describe the compound by describing the number and type of each atom in the simplest unit of the compound
molecules or ions
each element 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
polyatomic groups are placed in parentheses
if more than one
Tro's Introductory Chemistry, Chapter 5

7. Formulas Describe Compounds
water = H2O \ two atoms of hydrogen and 1 atom of oxygen
table sugar = C12H22O11 \12 atoms of C, 22 atoms of H and 11 atoms O
Tro's Introductory Chemistry, Chapter 5

8. Order of Elements in a Formula
metals written first
NaCl
nonmetals written in order from Table 5.1
CO2
are occasional exceptions for historical or informational reasons
H2O, but NaOH
Table 5.1
Order of Listing Nonmetals
in Chemical Formulas C P N H S I Br Cl O F
Tro's Introductory Chemistry, Chapter 5

9. Molecules with Polyatomic Ions
symbol of the polyatomic
ion called nitrate
ion called sulfate
Mg(NO3)2
compound called
magnesium nitrate
CaSO4
compound called
calcium sulfate
parentheses to group two NO3’s
no parentheses for one SO4
implied “1” subscript
on magnesium
on calcium
Tro's Introductory Chemistry, Chapter 5

10. Molecules with Polyatomic Ions
subscript indicating
two NO3 groups
no subscript indicating
one SO4 group
Mg(NO3)2
compound called
magnesium nitrate
CaSO4
compound called
calcium sulfate
implied “1” subscript
on nitrogen, total 2 N
on sulfur, total 1 S
stated “3” subscript
on oxygen, total 6 O
stated “4” subscript
on oxygen, total 4 O

11. 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

12. Molecular Elements H2 N2 O2 F2 Cl2 Br2 I2
Certain elements occur as 2 atom molecules
Rule of 7’s
there are 7 common diatomic elements
find the element with atomic number 7, N
make a figure 7 by going over to Group 7A, then down
don’t forget to include H2
VIIA 7 H2
N2 O F2
Cl2
Br2 I2

13. Tro's Introductory Chemistry, Chapter 5
Molecular Compounds
two or more nonmetals
smallest unit is a molecule
Tro's Introductory Chemistry, Chapter 5

14. 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

15. Molecular View of Elements and Compounds

16. Tro's Introductory Chemistry, Chapter 5
Classify each of the following as either an atomic element, molecular element, molecular compound or ionic compound
aluminum, Al
aluminum chloride, AlCl3
chlorine, Cl2
acetone, C3H6O
carbon monoxide, CO
cobalt, Co
Tro's Introductory Chemistry, Chapter 5

17. Tro's Introductory Chemistry, Chapter 5
Classify each of the following as either an atomic element, molecular element, molecular compound or ionic compound
aluminum, Al = atomic element
aluminum chloride, AlCl3 = ionic compound
chlorine, Cl2 = molecular element
acetone, C3H6O = molecular compound
carbon monoxide, CO = molecular compound
cobalt, Co = atomic element
Tro's Introductory Chemistry, Chapter 5

18. Is the compound one of the exceptions to the rules?
Formula-to-Name Step 1
Is the compound one of the exceptions to the rules?

19. Common Names - Exceptions
H2O = water, steam, ice
NH3 = ammonia
CH4 = methane
NaCl = table salt
C12H22O11 = table sugar
Tro's Introductory Chemistry, Chapter 5

20. What major class of compound is it? Ionic or Molecular
Formula-to-Name Step 2
What major class of compound is it?
Ionic or Molecular

21. Tro's Introductory Chemistry, Chapter 5
Major Classes
Ionic
metal + nonmetal
metal first in formula
Binary Ionic
compounds with polyatomic ions
Molecular
2 nonmetals
Binary Molecular (or Binary Covalent)
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

22. Formula-to-Name Step 3 What major subclass of compound is it?
Binary Ionic, Ionic with Polyatomic Ions,
Binary Molecular,
Binary Acid, Oxyacid

23. 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

24. Apply Rules for the Class and Subclass
Formula-to-Name Step 4
Apply Rules for the Class and Subclass

25. 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
Tro's Introductory Chemistry, Chapter 5

26. Monatomic Nonmetal Anion
determine the charge from position on the Periodic Table
to name anion, change ending on the element name to –ide
4A = -4
5A = -3
6A = -2
7A = -1
C = carbide
N = nitride
O = oxide
F = fluoride
Si = silicide
P = phosphide
S = sulfide
Cl = chloride
Tro's Introductory Chemistry, Chapter 5

27. Metal Cations Type I Type II
metals whose ions can only have one possible charge
IA, IIA, (Al, Ga, In)
determine charge by position on the Periodic Table
IA = +1, IIA = +2, (Al, Ga, In = +3)
Type II
metals whose ions can have more than one possible charge
determine charge by charge on anion
How do you know a metal cation is Type II?
its not Type I !!!
Tro's Introductory Chemistry, Chapter 5

28. 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.
lithium, Li
copper, Cu
gallium, Ga
tin, Sn
strontium, Sr
Tro's Introductory Chemistry, Chapter 5

29. 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.
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

30. Type I Binary Ionic Compounds
Contain Metal Cation + Nonmetal Anion
Metal listed first in formula & 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

31. Example – Naming Binary Ionic, Type I Metal CsF
Is it one of the common exceptions?
H2O, NH3, CH4, NaCl, C12H22O11 = No!
Identify Major Class
Cs = is a metal because it is on the left side of the PT
F = is a nonmetal because it is on the right side of the PT
 Ionic
Identify the Subclass
2 elements,  Binary Ionic
Is the metal Type I or Type II
Cs is in Group IA,  Type I
Tro's Introductory Chemistry, Chapter 5

32. Example – Naming Binary Ionic, Type I Metal CsF
Identify cation and anion
Cs = Cs+ because it is Group 1
F = F- because it is Group 7
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

33. Type II Binary Ionic Compounds
Contain Metal Cation + Nonmetal Anion
Metal listed first in formula & 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

34. Example – Naming Binary Ionic, Type II Metal CuCl
Is it one of the common exceptions?
H2O, NH3, CH4, NaCl, C12H22O11 = No!
Identify Major Class
Cu = is a metal because it is on the left side of the PT
Cl = is a nonmetal because it is on the right side of the PT
 Ionic
Identify the Subclass
2 elements,  Binary Ionic
Is the metal Type I or Type II
Cu is not in Group IA, IIA, or (Al, Ga, In)  Type II
Tro's Introductory Chemistry, Chapter 5

35. Example – Naming Binary Ionic, Type II Metal CuCl
Identify cation and anion
Cl = Cl- because it is Group 7
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

36. Determining the Charge on a Multivalent Cation – Au2S3
determine the charge on the anion
Au2S3 - the anion is S, since it is in Group 6A, its charge is -2
determine the total negative charge
since there are 3 S in the formula, the total negative charge is -6
determine the total positive charge
since the total negative charge is -6, the total positive charge is +6
divide by the number of cations
since there are 2 Au in the formula & the total positive charge is +6, each Au has a +3 charge
Tro's Introductory Chemistry, Chapter 5

37. Tro's Introductory Chemistry, Chapter 5
Examples
LiCl = lithium chloride
AlCl3 = aluminum chloride
PbO = lead(II) oxide
PbO2 = lead(IV) oxide
Mn2O3 = manganese(III) oxide
ZnCl2 = zinc(II) chloride or zinc chloride
AgCl = silver(I) chloride or silver chloride
Tro's Introductory Chemistry, Chapter 5

38. 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

39. Some Common Polyatomic Ions
Name
Formula
acetate
C2H3O2–
carbonate
CO32–
hydrogen carbonate
(aka bicarbonate)
HCO3–
hydroxide
OH–
nitrate
NO3–
nitrite
NO2–
chromate
CrO42–
dichromate
Cr2O72–
ammonium
NH4+
Name
Formula
hypochlorite
ClO–
chlorite
ClO2–
chlorate
ClO3–
perchlorate
ClO4–
sulfate
SO42–
sulfite
SO32–
hydrogensulfate
(aka bisulfate)
HSO4–
hydrogensulfite
(aka bisulfite)
HSO3–
Tro's Introductory Chemistry, Chapter 5

40. Patterns for Polyatomic Ions
elements in the same column form similar polyatomic ions
same number of O’s and same charge
ClO3- = chlorate \ BrO3- = bromate
if the polyatomic ion starts with H, the name adds hydrogen- prefix before name and add 1 to the charge
CO32- = carbonate \ HCO3-1 = hydrogencarbonate
Tro's Introductory Chemistry, Chapter 5

41. Periodic Pattern of Polyatomic Ions -ate groups
IIIA IVA VA VIA VIIA BO 3 -3 CO 3 -2 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
Tro's Introductory Chemistry, Chapter 5

42. Patterns for Polyatomic Ions
-ate ion
chlorate = ClO3-1
-ate ion + 1 O  same charge, per- prefix
perchlorate = ClO4-1
-ate ion – 1 O  same charge, -ite suffix
chlorite = ClO2-1
-ate ion – 2 O  same charge, hypo- prefix, -ite suffix
hypochlorite = ClO-1
Tro's Introductory Chemistry, Chapter 5

43. Example – Naming Ionic with Polyatomic Ion Na2SO4
Is it one of the common exceptions?
H2O, NH3, CH4, NaCl, C12H22O11 = No!
Identify Major Class
Na = is a metal because it is on the left side of the PT
SO4 = 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 IA,  Type I
Tro's Introductory Chemistry, Chapter 5

44. Example – Naming Ionic with Polyatomic Ion Na2SO4
Identify the ions
Na = Na+ because in Group 1
SO4 = SO42- a polyatomic ion
Name the cation
Na+ = sodium (Type I)
Name the anion
SO42- = sulfate
Write the name of the cation followed by the name of the anion
sodium sulfate
Tro's Introductory Chemistry, Chapter 5

45. Example – Naming Ionic with Polyatomic Ion Fe(NO3)3
Is it one of the common exceptions?
H2O, NH3, CH4, NaCl, C12H22O11 = No!
Identify Major Class
Fe = is a metal because it is on the left side of the PT
NO3 = 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
Fe is not in Group IA, IIA, or (Al, Ga, In)  Type II
Tro's Introductory Chemistry, Chapter 5

46. Example – Naming Ionic with Polyatomic Ion Fe(NO3)3
Identify the ions
NO3 = NO3- a polyatomic ion
Fe = Fe+3 to balance the charge of the 3 NO3-1
Name the cation
Fe+3 = iron(III) (Type II)
Name the anion
NO3- = nitrate
Write the name of the cation followed by the name of the anion
iron(III) nitrate
Tro's Introductory Chemistry, Chapter 5

47. 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

48. Binary Molecular Compounds of 2 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

49. Tro's Introductory Chemistry, Chapter 5
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

50. Example – Naming Binary Molecular BF3
Is it one of the common exceptions?
H2O, NH3, CH4, NaCl, C12H22O11 = No!
Identify Major Class
B = is a nonmetal because it is on the right side of the PT
F = is a nonmetal because it is on the right side of the PT
 Molecular
Identify the Subclass
2 elements  Binary Molecular
Tro's Introductory Chemistry, Chapter 5

51. Example – Naming Binary Molecular BF3
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
Tro's Introductory Chemistry, Chapter 5

52. Tro's Introductory Chemistry, Chapter 5
Acids
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

53. 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

54. Example – Naming Binary Acids HCl
Is it one of the common exceptions?
H2O, NH3, CH4, NaCl, C12H22O11 = No!
Identify Major Class
first element listed is H,  Acid
Identify the Subclass
2 elements,  Binary Acid
Tro's Introductory Chemistry, Chapter 5

55. Sample - Naming Binary Acids – HCl
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

56. Example – Naming Oxyacids H2SO4
Is it one of the common exceptions?
H2O, NH3, CH4, NaCl, C12H22O11 = 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

57. Example – Naming Oxyacids H2SO4
Identify the anion
SO4 = SO42- = sulfate
If the anion has –ate suffix, change it to –ic. If the anion has –ite suffix, change it to -ous
SO42- = sulfate  sulfuric
Write the name of the anion followed by the word acid
sulfuric acid
(kind of an exception, to make it sound nicer!)
Tro's Introductory Chemistry, Chapter 5

58. Example – Naming Oxyacids H2SO3
Is it one of the common exceptions?
H2O, NH3, CH4, NaCl, C12H22O11 = 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

59. Example – Naming Oxyacids H2SO3
Identify the anion
SO3 = SO32- = sulfite
If the anion has –ate suffix, change it to –ic. If the anion has –ite suffix, change it to -ous
SO32- = sulfite  sulfurous
Write the name of the anion followed by the word acid
sulfurous acid
Tro's Introductory Chemistry, Chapter 5

60. Formula-to-Name Flow Chart

61. Name – to – Formula

62. Writing the Formulas from the Names
For binary molecular compounds, use the prefixes to determine the subscripts
For Type I, Type II, Ternary Compounds and Acids
Determine the ions present
Determine the charges on the cation and anion
Balance the charges to get the subscripts
Tro's Introductory Chemistry, Chapter 5

63. Example – Binary Molecular dinitrogen pentoxide
Identify the symbols of the elements
nitrogen = N
oxide = oxygen = O
Write the formula using prefix number for subscript
di = 2, penta = 5
N2O5
Tro's Introductory Chemistry, Chapter 5

64. Compounds that Contain Ions
compounds of metals with nonmetals are made of ions
metal atoms form cations, nonmetal atoms for anions
compound must have no total charge, therefore we must balance the numbers of cations and anions in a compound to get 0 charge
if Na+ is combined with S2-, you will need 2 Na+ ions for every S2- ion to balance the charges, therefore the formula must be Na2S
Tro's Introductory Chemistry, Chapter 5

65. 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 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

66. 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 other ion
Reduce subscripts to smallest whole number ratio
Check that the total charge of the cations cancels the total charge of the anions
Al+3 column IIIA
O2- column VIA
Al+3 O2-
Al2 O3
Al = (2)∙(+3) = +6
O = (3)∙(-2) = -6
Tro's Introductory Chemistry, Chapter 5

67. Tro's Introductory Chemistry, Chapter 5
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

68. Tro's Introductory Chemistry, Chapter 5
Practice - What are the formulas for compounds made from the following ions?
K+ with N3- K3N
Ca+2 with Br- CaBr2
Al+3 with S2- Al2S3
Tro's Introductory Chemistry, Chapter 5

69. Example – Ionic Compounds 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 other ion
Reduce subscripts to smallest whole number ratio
Check that the total charge of the cations cancels the total charge of the anions
Mn+4
S2-
Mn+4 S2-
Mn2S4
MnS2
Mn = (1)∙(+4) = +4
S = (2)∙(-2) = -4
Tro's Introductory Chemistry, Chapter 5

70. Example – Ionic Compounds 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 other ion
Reduce subscripts to smallest whole number ratio
Check that the total charge of the cations cancels the total charge of the anions
Fe+3
PO43-
Fe+3 PO43-
Fe3(PO4)3
FePO4
Fe = (1)∙(+3) = +3
PO4 = (1)∙(-3) = -3
Tro's Introductory Chemistry, Chapter 5

71. Example – Ionic Compounds ammonium carbonate
Write the symbol for the cation and its charge
Write the symbol for the anion and its charge
Charge (without sign) becomes subscript for other ion
Reduce subscripts to smallest whole number ratio
Check that the total charge of the cations cancels the total charge of the anions
NH4+
CO32-
NH4+ CO32-
(NH4)2CO3
(NH4)2CO3
NH4 = (2)∙(+1) = +2
CO3 = (1)∙(-2) = -2
Tro's Introductory Chemistry, Chapter 5

72. Tro's Introductory Chemistry, Chapter 5
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
aluminum ion with a sulfate ion
Tro's Introductory Chemistry, Chapter 5

73. Tro's Introductory Chemistry, Chapter 5
Practice - What are the formulas for compounds made from the following ions?
Cu2+ with N3- Cu3N2
Fe+3 with Br- FeBr3
Al+3 with SO42- Al2(SO4)3
Tro's Introductory Chemistry, Chapter 5

74. Example – Binary Acids hydrosulfuric acid
in all acids the
cation is H+
Write the symbol for the cation and its charge
Write the symbol for the anion and its charge
Charge (without sign) becomes subscript for other ion
Reduce subscripts to smallest whole number ratio
Check that the total charge of the cations cancels the total charge of the anions H+
hydro means
binary
S2-
H+ S2-
H2S
H2S
H = (2)∙(+1) = +2
S = (1)∙(-2) = -2
Tro's Introductory Chemistry, Chapter 5

75. Example – Oxyacids carbonic acid
in all acids the
cation is H+
Write the symbol for the cation and its charge
Write the symbol for the anion and its charge
Charge (without sign) becomes subscript for other ion
Reduce subscripts to smallest whole number ratio
Check that the total charge of the cations cancels the total charge of the anions H+
no hydro means
polyatomic ion
CO32-
-ic means -ate ion
H+ CO32-
H2CO3
H2CO3
H = (2)∙(+1) = +2
CO3 = (1)∙(-2) = -2
Tro's Introductory Chemistry, Chapter 5

76. Practice - What are the formulas for the following acids?
chlorous acid
phosphoric acid
hydrobromic acid
Tro's Introductory Chemistry, Chapter 5

77. Practice - What are the formulas for the following acids?
H+ with ClO2– HClO2
H+ with PO43– H3PO4
H+ with Br– HBr
Tro's Introductory Chemistry, Chapter 5

78. 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 H2O
= 2(1.01 amu H) amu O = amu
Tro's Introductory Chemistry, Chapter 5