1. 6.4 - NOTES Naming and Writing Ionic Formulas

2. Ions and Ionic Compounds
Atoms that have a charge; can be positive or negative
Formed when an atom gains or loses electrons
Metals tend to lose electrons to form positive ions
 These ions are also called cations
Nonmetals tend to gain electrons to form negative ions
  These ions are also called anions

3. Polyatomic ions NH4+1 C2H3O2-1
An ion consisting of bonded atoms with a single charge
Can be positive or negative
They always stay together and can NEVER be split up
Some examples are
NH4+1 C2H3O2-1

4. Ionic compounds Made of positive and negative ions
The overall charge of an ionic compound is 0 (neutral)

5. Writing formulas
The cation (metal) is first, then the anion (non-metal). The total charge must be zero, so we use subscripts to indicate the number of ions. The ions must have the smallest ratio possible.

6. Examples
Sodium and bromine
Na+1 Br-1 NaBr
calcium and fluorine
Ca+2 F-1 CaF2

7. Potassium and oxygen
K+1 O-2 K2O
barium and sulfur
Ba+2 S-2 BaS

8. Aluminum and chlorine
Al+3 Cl-1 AlCl3
magnesium and nitrogen
Mg+2 N-3 Mg3N2

9. Naming Compounds
Monatomic cations are known by their name. For example, Na+ is sodium
Monatomic anions have the ending “ide,” which means negative. For example, O-2 is known as oxide. Polyatomic ions have their normal names.

10. Examples
RbNO2
Rubidium Nitrite
CuSO4
Copper (II) Sulfate

11. Writing formulas from names
Using the given names, the cation comes first and the anion comes second.
Remember the ending –ide usually means it is a single element, while the endings –ite and –ate indicate a polyatomic ion
Some metals have multiple charges, like copper and gold. To indicate the difference in the charge on the ions, Roman numerals are used to indicate the form of the ion present in the formula.
Gold (III) chloride vs. gold (I) chloride
Au+3 Cl-1  AuCl3
Au+1 Cl-1  AuCl

12. Ca(HSO4)2
Calcium Bisulfate
Calcium Hydrogen Sulfate
(NH4)3PO4
Ammonium Phosphate

13. Al2(SO3)3
Aluminum Sulfite
Ag(CO3)2
Silver Carbonate