I
II
III IV

 Chemical formulas indicate the elements involved and how many of each type are in the molecule.
C
8
H
18 subscripts
Al
2
(SO
4
)
3

Types of Ions
 Monatomic Ions – one element

Criss-Cross Method
Used to write formulas of ionic compounds (salts)
Step 1: List Charges of each ion
Step 2: Criss-Cross the # of the Charge only!
Step 3: Simplify (Never write a subscript of 1)

Criss-Cross means:
•
# of the Charge of cation
•
# of the Charge of anion subscript of the anion .
subscript of the cation.

Types of Ions
 Polyatomic – more than one element

Example: Calcium Phosphate
Use parentheses for a polyatomic ion.
Ca = 2+ PO
4
= 3-
Ca
3
(PO
4
)
2

Lowest Whole Number Ratio of Elements
CaSO
4
= 1 calcium ion for every 1 sulfate ion
Na
2
SO
4
= 2 sodium ions for every 1 sulfate ion

*Stock System of Naming
Compounds
Roman numeral matching the charge is used.
Ex: Cu +1 , copper I
Cu +2 , copper II
Cu +2 N0
3
: Cu(N0
3
)
2
Cu + NO
3
: CuNO
3 copper II nitrate copper I nitrate

Naming Binary Ionic Compounds

Cation: Name the Metal (use Roman numerals for transition metals)

Anion: nonmetal Change the ending to –ide.
Calcium Chloride
Barium Oxide
Potassium Sulfide
Iron (III) Bromide
Chromium (III) Oxide

Traditional Naming of Ionic
Compounds
Traditional naming of ionic compounds used the
Latin names or some common names and a suffix corresponding to the charge as follows.
Copper: Cuprum
Cu +1 : cuprous Cu +2 : cupric
The ous ending was used with the lower charged ion.
The ic ending was used with the higher charged ion.

Ferrous Nitrate : Iron +2, nitrate: Fe(NO
3
)
2
Plumbic Chloride: Lead +4, chlorine: PbCl
4
Latin Names:
Ferrum – Iron, Cuprum – Copper,
Stannum – Tin, Mercurum – Mercury
Common Names: Any element with more than one possible charge: lead, mercury, tin, etc.

*Examples of Naming for Polyatomic Ions
Calcium Sulfite
Barium Phosphate
Ammonium Sulfide
Iron (III) Sulfite

Same rules
EXCEPT include prefixes
NEVER start a compound name with mono-
(drop the prefix)
1 = mono 2 = di
3 = tri 4 = tetra
5 = penta 6 = hexa
7 = hepta 8 = octa
9 = nona 10 = deca

NO
2
= nitrogen dioxide
BF
3
= boron trifluoride
P
2
O
5
= diphosphorus pentoxide

Indicates how many atoms are in a single molecule of the compound.
C
6
H
12
O
6
= glucose
6 carbon atoms
12 hydrogen atoms
6 oxygen atoms

 Binary Acids: Contain only two elements.
 Hydrogen & a nonmetal
 Hydro- ____________ -ic acid.
Ex: HCl = Hydrochloric Acid
H
2
S = Hydrosulfuric Acid

 Binary Salts: Contain only two elements.
 A metal & a nonmetal
 Name the metal & change the ending on the non-metal to –ide.
Ex: NaCl = Sodium Chloride
MgBr
2
= Magnesium Bromide

 Ternary Acids: Prefix & Suffix
 X could be any element other than (Sulfur,
Phosphorus, Nitrogen or Carbon)
 HXO = hypo-________-ous
 HXO
2
 HXO
3
 HXO
4
= __________-ous
= __________-ic
= per-_________-ic

 Example:
 HClO = hypochlorous acid
 HClO
2
 HClO
3
 HClO
4
= chlorous acid
= chloric acid
= perchloric

 Ternary Salts: Prefix & Suffix
 X could be any element other than (Sulfur,
Phosphorus, Nitrogen or Carbon)
 XO = hypo-________-ite
 XO
2
-
 XO
3
-
 XO
4
-
= __________-ite
= __________-ate
= per-_________-ate

 Example; Chlorine (X represents any metal)
 XClO = hypochlorite
 XClO
2
-
 XClO
3
-
 XClO
4
-
= chlorite
= chlorate
= perchlorate