Molecules and Compounds 5
Chapter Overview
Chapter 5 introduces the students to predicting and writing chemical formulas. They will
also learn how to derive the name of a molecule from the formula and the type of species. The
naming of ionic compounds, molecular compounds, and acids will be explained.
Lecture Outline
5.1 Sugar and Salt
5.2 Compounds Display Constant Composition
Learning Objective: Restate and apply the law of constant composition.
A. Every sample of a compound has the same proportions of constituent elements
5.3 Chemical Formulas: How to Represent Compounds
Learning Objective: Write chemical formulas.
Learning Objective: Determine the total number of each type of atom in a chemical
formula.
A. Subscripts in formula represent relative number of each type of atom in the molecule
B. Order for listing nonmetal atoms: C, P, N, H, S, I, Br, Cl, O, F
C. Groups of atoms are set off by parentheses, e.g. Mg(NO3)2
D. Types of Chemical Formulas
1. Empirical
3. Structural
5.4 A Molecular View of Elements and Compounds
Learning Objective: Classify elements as atomic or molecular.
Learning Objective: Classify compounds as ionic or molecular.
A. Atomic elements exist in nature as single atoms
B. 7 molecular elements exist as diatomic molecules: H2, N2, O2, F2, Cl2, Br2, I2
C. Molecular compounds are formed between two or more nonmetals
D. Ionic compounds are formed between a metal and one or more nonmetals
5.5 Writing Formulas for Ionic Compounds
5.6 Nomenclature: Naming Compounds
Learning Objective: Distinguish between common and systematic names for compounds.
A. Systematic name; e.g., sodium chloride
B. Common name; e.g., table salt
5.7 Naming Ionic Compounds
Learning Objective: Name binary ionic compounds containing a metal that forms only
one type of ion.
Learning Objective: Name binary ionic compounds containing a metal that forms more
than one type of ion.
Learning Objective: Name ionic compounds containing a polyatomic ion.
A. Type I compounds
2. Most main group metals form type I compounds
B. Naming type I binary ionic compounds
1. Name of cation (metal) + (base name of anion + ide)
2. Example, NaCl is sodium chloride
C. Type II compounds
2. Transition metals usually, but not exclusively, form type II compounds
D. Naming type II binary ionic compounds
1. Name of cation + (charge of cation) + (base name of anion + ide)
2. Charge of cation given in roman numerals
3. Example, FeCl3 is iron (III) chloride
E. Naming ionic compounds containing a polyatomic ion
1. Use the same procedure as ionic compounds
3. Example, NaNO3 is sodium nitrate
5.8 Naming Molecular Compounds
Learning Objective: Name molecular compounds.
5.9 Naming Acids
Learning Objective: Name binary acids.
Learning Objective: Name oxyacids containing an oxyanion ending in –ate.
Learning Objective: Name oxyacids containing an oxyanion ending in –ite.
A. Acids are molecular compounds that dissolve in water to form H+ ions
B. Binary acids
3. Example, HCl is hydrochloric acid
C. Oxyacids
1. Hydrogen and polyatomic oxyanion
2. Oxyanions ending with –ate
3. Oxyanions ending with –ite
5.10 Nomenclature Summary
Learning Objective: Recognize and name chemical compounds.
5.11 Formula Mass: The Mass of a Molecule or Formula Unit
Learning Objective: Calculate formula mass.
A. Formula mass = mass of atom 1 × number of first element in molecule + mass of atom
2 × number of second element + …
B. Example, formula mass of CCl4 = 1 × (12.01 amu) + 4 × (35.45 amu) = 153.81 amu
Chemical Principle Teaching Ideas
Compounds
To illustrate the universal makeup of a compound, show examples of different forms of
the same molecule. Showing a sample of solid, liquid, and gaseous water and explaining that the
ratio of hydrogen atoms to oxygen atoms is the same will help teaching the concept.
Chemical Formulas
Emphasize that all molecules are composed of atoms in small, whole-number ratios.
Chemical Nomenclature
Students have trouble remembering which rules fit for which kind of molecule. Give the
Skill Builder Solutions
4.3 g O 7.5 g O
5.4. a. Molecular element; chlorine is one of the 7 species that exist as diatomic species.
b. Molecular compound; this species contains two different nonmetals, so it is a
compound.
c. Atomic element; gold is a monatomic element.
Plus. The cation is zinc, and the anion is nitrogen, which becomes nitride, for the correct
name zinc nitride.
Suggested Demonstrations
Bring in a set of molecular models and make a few of the oxyanion groups. Then, bond them
with different species illustrating their combinatory nature.
Reaction of Sodium and Chlorine, Chemical Demonstrations 1:61, Shakhashiri, B.Z. University
Guided Inquiry Ideas
Below are a few example questions that students answer in the guided inquiry activities provided
in the Guided Activity Workbook.
How do you know that carbon monoxide and carbon dioxide are molecular compounds and not
ionic?
In any stable ionic compound, what is the relationship between the total positive and total
negative charge?
How does the name of the second atom in a formula for a molecular compound compare to the
name of that atom?