Honors Chemistry
Chapter 5 notes—Types of Compounds
I. Oxidation numbers
A. Oxidation number—a number that indicates the number of electrons an atom will gain, lose, or
share when bonding
1. Free elements have an oxidation number of zero
a. Most elements are truly free
b. 7 naturally occurring diatomic elements
1) Hydrogen
2) Nitrogen
3) Oxygen
4) Fluorine
5) Chlorine
6) Bromine
7) Iodine
2. Family 1 always has an oxidation number of +1
3. Family 2 always has an oxidation number of +2
4. Hydrogen always has an oxidation number of +1, except as a hydride, -1
5. Oxygen always has an oxidation number of -2, except as a peroxide, -1
6. The sum of the oxidation numbers in a compound is zero
7. The oxidation number of an ion is equal to its charge
8. Families 13-17 are fairly predictable
9. Families 3-12 are not predictable except that they will be positive
B. Oxidation numbers are used to write formulas
1. Identify the oxidation numbers
2. Using the absolute value, choose the LCM of the oxidation numbers
3. the subscript equals the LCM divided by the oxidation number of the element
4. Formulas are written in the lowest ratio possible
II. Ionic compounds
A. Binary Ionic compounds
1. Intro
a. contain only two elements bonded ionically
b. formula indicates the formula unit, the repeating pattern
2. Naming
a. Make sure that the elements are written in proper order
1)metal then nonmetal
2) positive oxidation number then negative oxidation number
b. Write the name of the metal
c. Change the ending of the second element, the non-metal, to -ide
d. Write the name of the non-metal with the change
3. Formulas
a. Write the elements in proper order
b. Use the LCM method from oxidation numbers to obtain correct subscripts (see I. B)
c. Make sure that the subscripts are written in lowest terms, this represents the formula unit
4. Formula Unit
a. the repeating pattern in an ionic compound
b. the simplest ratio of ions in an ionic compound
D. Polyatomic ions
1. an ion with two or more elements
2. the atoms within the ion are covalently bonded
3. polyatomic ion acts a group, do not change the subscripts within the ion
4. name like a binary, only do not change the name of the polyatomic ion
5. memorize the polyatomic ions on p. 157
6. write formula like the binary compounds, use parentheses if a subscript is need for the ion
E. Transition element compounds
1. They have multiple positive oxidation states
2. Zinc is always +2 and silver is always +1
3. The stock system or Roman numeral system is used in naming.
a. a roman numeral is placed in parenthesis after the element
b. the roman numeral indicates the positive oxidation number, ex. Cu (I)
c. the roman numeral is used in both the name and the formula
F. Hydrates
1. Compounds that have water as part of their crystalline structure
2. Hygroscopic compound—compound that easily absorbs water from the air
3. Deliquescent—hygroscopic compound that absorbs so much water that it dissolves to form a
solution
4. Anydrous—compound that has had all the water removed
4. Formulas
a. Ionic compound plus a dot and H2O
b. CaSO4 · 2 H2O
c. naming
calcium sulfate dihydrate
d. Prefixes (see p. 165)
G. Formulas
1. Coefficient—number before the formula indicating number of molecules or formula units
2. subscript—number after an element indicating number of atoms in the molecule or number of
particles within a parenthesis
III. Covalent compounds
A. Distillation—method of separating substances in a mixture by evaporation of a liquid and the
condensation of the vapor
B. Molecular Elements—elements that form molecules when by themselves
1. Diatomic molecules—two atoms of the same element
2. Allotropes—molecules of a single element that differ in molecular structure
a. Phosphorus
1) three different forms—red, white, and black
2) structures are all different
b. Carbon
1) Diamond
2) Graphite
3) Carbon blacks
4) Charcoal
5) fullerenes
6) linear acetylenic carbon
c. Oxygen
1) diatomic
2) triatomic (ozone)
3 Naming
a. Name like an ionic compound—ending is –ide
b. Use prefixes to indicate number of atoms
1) Mono is not to be used on the first element
2) In double vowel combos, first of the pair is omitted
4. Writing formulas
a. Indicate elements in order
b. use subscripts to indicate number of atoms according to prefixes
5. Common names
a. Some have common names that are so familiar those names are used—water, ammonia
b. Use names based on your audience
IV. Acids—aqueous compounds
A. Binary acids
1. Structure is HX
2. Name
a. starts with hydro
b. name of the non-metal
c. add ending of -ic to the non-metal
d. end with acid
B. Polyatomic acids
1. Structure is H(polyatomic)
2. Name
a. starts with polyatomic name
b. change ite to ous and ate to ic
c. end with acid
V. Organic compounds
A. Organic compound—compounds that have carbon as their basis, usually found in living things
B. Inorganic compound—compounds that do not contain carbon.
C. Hydrocarbons—simplest organics that have only carbon and hydrogen
D. Naming system will be discussed in a later chapter. There is a unique naming system for these
compounds however.