1. Names and formulas for ionic compounds
Chapter 7.3

2. Formulas for ionic compounds
Ionic compounds are made up of ions arranged in a repeating pattern
Formula unit: chemical formula for an ionic compound
Represents the simplest ratio of the ions involved
Formula unit of magnesium chloride = MgCl2
Magnesium and chloride ions exist in a 1:2 ratio
Overall charge is zero

3. Monatomic ions One-atom ions Examples: Mg2+, Br -, Al3+, O2-
Binary ionic compounds are composed of two parts:
Positively charged monatomic ion of a metal
Negatively charged monatomic ion of a nonmetal

4. Oxidation numbers The charge of a monatomic ion
Example: Mg2+ - oxidation number = 2+
The oxidation number of an element in an ionic compound is the number of electrons transferred from or to the atom to form the ion

5. Formulas for binary ionic compounds
In the chemical formula for any ionic compound, the symbol of the cation (+) is written first, followed by the symbol of the anion (-)
Subscripts (small numbers on the lower right of the symbol) represent the number of ions of each element in the ionic compound. If no subscript is written, it is assumed to be one.
Example – MgCl2
Remember that the overall charge of the compound in zero (neutral)
1 Mg2+ cation
2 Cl - anions

6. POLYATOMIC IONS Ions containing more than one atom Examples
Page 221 Table 7.9
Make flashcards for every polyatomic ion
Quizzes on these can occur at any time for the rest of the year
You must know the names, formulas & charges

7. Formulas for polyatomic ionic compounds
Polyatomic ions: made up of more than one atom
A polyatomic ion acts as an individual ion in a compound and its charge applies to the ENTIRE group of atoms
Never change the subscripts of the atoms within the ion
If more than one is needed to form a compound, place parentheses around the ion and write the appropriate subscript outside of the parentheses
Example – Ca(OH)2
1 Ca2+ cation
2 OH - polyatomic anions

8. Names for ions and ionic compounds
Oxyanion: a polyatomic ion composed of an element, usually a nonmetal, bonded to one or more oxygen atoms
Names for oxyanions containing sulfur & nitrogen
Identify the ion with the greatest number of oxygen atoms. This ion is named using the root of the nonmetal and the suffix –ate
Identify the ion with the fewer number of oxygen atoms. This ion is named using the root of the nonmetal and the suffix –ite
Examples:
NO3- = nitrate ; NO2- = nitrite
SO42- = sulfate ; SO32- = sulfite

9. Names for ions and ionic compounds
Names for oxyanions containing chlorine
Greatest number of oxygen atoms: Perchlorate = ClO4-
One fewer oxygen atom: Chlorate = ClO3-
Two fewer oxygen atoms: Chlorite = ClO2-
Three fewer oxygen atoms: Hypochlorite = ClO -

10. Naming ionic compounds
Name the cation ( + ) followed by the anion ( - )
For monatomic cations, use the element name
For monatomic anions, use the root of the element name plus the suffix –ide
CsBr --- Cesium bromide

11. Naming ionic compounds
To distinguish between multiple oxidation numbers of the same element (transition metals), the chemical formula number must indicate the oxidation number of the cation in roman numerals
Applies only to transition metals and metals on the right side of the periodic table (NOT group 1 and group 2 metals)
Fe2+ and O2- form FeO – iron (II) oxide
Fe3+ and O2- form Fe2O3 – iron (III) oxide

12. Naming ionic compounds
When a compound contains a polyatomic ion, simply name the cation followed by the name of the polyatomic ion
NaOH = sodium hydroxide
(NH4)2S = ammonium sulfide

13. NaBr Sodium bromide Binary ionic compound:
Composed of 2 monatomic ions
Sodium
bromide
Ending with -ide
Root of the element Bromine

14. Oxidation number of copper
Cu(NO3)2
Transition metal
&
Polyatomic ion
Check Table 7.8
(page 219)
Some metal ions have multiple oxidation numbers. If one does, you must indicate it when naming the compound that it is in
Copper
(II)
nitrate
Oxidation number of copper
Polyatomic anion

15. Ag2CrO4 Silver chromate Transition metal & Polyatomic ion
Check Table 7.8
(page 219)
Some metal ions have multiple oxidation numbers. If one does, you must indicate it when naming the compound that it is in
Silver
chromate
Polyatomic anion

16. NH4ClO4 Ammonium perchlorate Two Polyatomic ions Polyatomic anion
Polyatomic cation