1. Chapter 9:
Chemical formulas indicate the relative number of atoms of each kind in a chemical compound.
ex: C8H18  8 Carbon atoms, 18 Hydrogen atoms
Al2(SO4)3  2 Aluminum atoms, 3 Sulfur atoms, and
12 Oxygen atoms
Naming Ions
ions formed from a single atom are called monatomic ions.
Cations: losing electron(s) to form positive ions.
K+  potassium cation
Mg2+  magnesium cation
Anions: gaining electron(s) to form negative ions.
F1-  fluoride anion
N3-  nitride anion

2. Zn2+ I1- Zn I 2 Writing Ionic Compounds
compounds composed of two different elements are known as binary compounds.
the total numbers of positive and negative charges must be equal.
Criss-Cross Method
Write the formula for the compound zinc iodide.
zinc cation iodide anion
Zn2+
I1-
Zn I 2
Write the formulas for the following binary ionic compounds:
Silver chloride Zinc oxide Calcium bromide
AgCl
ZnO
CaBr2

3. The Stock System
most transition metals can form two or more cations with different charges. Roman numerals indicate the charge.
ex: iron (II)  Fe2+
iron (III)  Fe3+
Polyatomic Ions
Ex: Carbonate anion  (CO3)2-
Nitrate anion  (NO3)1-
Write the formulas for the following ionic compounds.
Sodium carbonate Calcium nitrate Iron(II)sulfate
Na2CO3
Ca(NO3)2
FeSO4

4. Naming Binary Molecular Compounds
molecular compounds are made of individual covalently bonded units, or molecules.
when naming molecules use prefixes to indicate the number of atoms present.
This is a totally different naming system……..DON’T MIX IT UP WITH IONIC COMPOUNDS!
# of atoms
Prefix 1
mono 6
hexa 2 di 7
hepta 3
tri 8
octa 4
tetra 9
nona 5
penta 10
deca

5. Ex: Name the following molecules.
SO3
ICl3
PBr5
As2O5
Sulfur trioxide
Iodine trichloride
Phosphorus pentabromide
Diarsenic pentoxide

6. Naming Acids
Types
Binary Acids: an acid containing H + (halogen)
Oxyacids: an acid that contains H + O + (nonmetal)
Rules for naming acids
Identify the ion within the acid.
Change the anion ending to one of the following:
Anion ending
In acid, replace with:
Examples
-ide
Hydro_____ic
acid
Hydrochloric
Acid, HCl
-ite
________ ous acid
Nitrous acid, HNO2
-ate
_______ic
Sulfuric Acid, H2SO4

7. REMINDER…………. HEED THESE TIPS! “BLAST FROM THE PAST”
There are so many formulas, how do I identify them?
IONIC COMPOUNDS  Metal + Nonmetal (NAME THE IONS!!!)
COVALENT MOLECULES  Nonmetal + Nonmetal (USE PREFIXES!!!)
ACIDS  H + (nonmetals) (USE THE CHART!!!)
“BLAST FROM THE PAST”
Cuprous vs Cupric……..Ferrous vs Ferric
“ic” is the higher of the two charges
“ous” is the lower of the two charges

8. Using Chemical Formulas
Formula Mass: the sum of the average atomic masses in a molecule or compound.
Ex: Write the formula for potassium chlorate and find its formula mass.
Potassium chlorate  KClO3
Formula mass = K (39.1amu) + Cl (35.5amu) + 3O (3x16amu)
= amu
Write the formula and determine the formula mass.
Magnesium chloride 
Calcium nitrate 
Barium hydroxide 
MgCl2 = 95.2 amu
Ca(NO3)2 = amu
Ba(OH)2 = amu