1. Names & Formulas
Ionic Compounds
8.3

2. Formulas Formula unit is the ratio of cations to anions’
Total number of electrons lost by cations must equal total number of electrons gained by anions
Binary compounds = simplest compound = 2 atoms
One cation, one anion
Monatomic ion = ion made from one atom

3. Typical Ions See Book, page 221
Oxidation number = oxidation state = number of electrons transferred from an atom to make a compound
Na+ oxidation number = +1
O2- oxidation number = 2-
Used to determine compound formulas

4. Formula Names
Remember: total number of electrons lost by cations must equal total number of electrons gained by anions!
Metal name is stated first.
Number of cations in ratio is subcripted
Nonmetal name is stated second
Suffix –ide is used
Number of anions in ration is subscripted

5. Formula Names Examples Sodium (Na+) and Chlorine (Cl-)
NaCl = ratio 1:1
Sodium Chloride
Calcium (Ca2+) and Fluorine (Fl-)
CaFl2 = ratio 1:2
Calcium Fluoride
Aluminum (3+) and Sulfur (2-)
Find lowest common dominator
(6)
2(Al 3+) + 3 (S 2+) = both transfer 6 electrons
Al2S3
Aluminum Sulfide

6. Formulas with Polyatomic Ions
Poly atomic ions stay together as a single group
Example Calcium and Phosphate
Calcium (2+)
Phosphate PO4 (3-)
3 (Ca) + 2 ( PO4)
Ca3(PO4)2
Calcium Phosphate

7. Naming Polyatomic Compounds
Oxyanions = polyatomic anions with one or more oxygen atom
With 2 anion forms:
Anion with most oxygen atoms is –ate
Anion with fewer oxygen atoms is –ite
With multiple anion forms:
Most oxygen atoms is per- metal -ate
Second most oxygen is –ate
Third most oxygen atoms is –ite
Fourth most oxygen atoms is hypo- metal -ite

8. Naming Review Name cation first, anion second
Monatomic ions use atom name
Monatomic anions take root of name and add –ide suffix
Group 1A and 2A metals have only one oxidation state. Transition metals can have more than one. Put oxidation state in as roman numerals
Polyatomic ions – just name the ion