1. Chapter 19.2 Chemical Formulas
Oxidation Numbers
Writing Chemical Formulas
Ionic Compounds
Naming Ionic & Covalent Compounds
Empirical and molecular Formulas

2. Oxidation Numbers
An oxidation number indicates how many electrons will be lost, gained or shared when bonding occurs
ALL COMPOUNDS have an electrical charge of ZERO
When the oxidation numbers are added up for all of the atoms in a compound, the answer equals zero

3. Oxidation Numbers & the Periodic Table
You can use the periodic table to predict the oxidation numbers for some of the groups.
The transition metals are an exception, they have variable oxidation numbers
Periodic Table

4. Writing Chemical Formulas for Ionic compounds
Write the symbol for the positive . monatomic ion. (Groups 1, 2, & 13)
Write the symbol for the negative monatomic ion. (Groups 15, 16, & 17)
Add superscripts so that the sum of the oxidation numbers equals zero

5. Writing a Chemical Formula
CrissCross Applesauce is all you need to know

6. Ionic Compounds Polyatomic Ions
Most Ionic compounds are made up of more than 2 types of atoms called Polyatomic Ions. (see table on p. 337)
Treat them just as you would when working with monatomic ions, except you need to put the polyatomic ion in brackets and place the oxidation number as a superscript on the outside of the bracket.

7. Naming monatomic Ionic Compounds
Write the root name of the second element
Add “ide” to the root name
Write the name of the first element in the compound
Ex: Na + Cl = NaCl, Naming this chemical formula would be , Sodium plus Chlorine equals Sodium chloride.

8. Naming Compounds with Polyatomic Ions
Write the name of the positive ion first
Write the name of the negative ion second
You can use the periodic table or an ion chart to get the names- There is one on p. 337 of your text book.
Treat them just as you would the monatomic ions.

9. Empirical Formula
The simplest whole number ratio by which the elements combine.
Ex: Hydrogen peroxide, each molecule contains 2 hydrogen and two oxygen atoms, but the empirical formula is HO

10. Molecular Formula
A molecular formula contains the actual number of atoms for each element in one molecule of the compound
Ex: Hydrogen peroxide, each molecule contains 2 hydrogen and two oxygen atoms, and the molecular formula is H2O2