1. Chapter 13
Chemical Formulas

2. Chemical Bonding
Strong attractive force between atoms or ions in a molecule or compound.
Formed by:
transferring e- (losing or gaining)
sharing e-

3. Ne Chemical Bonding Octet Rule
most atoms form bonds in order to have 8 valence e-
full outer energy level
like the Noble Gases!
Stability is the driving force behind bond formation! Ne

4. Chemical Formulas & Charge
All compounds have an electrical charge of zero (they are neutral).
An oxidation number indicates the charge on the atom (or ion) when electrons are lost, gained, or shared in chemical bonds.
In this class, we will refer to the charge.

5. Chemical Formulas & Charge
A sodium atom always ionizes to become Na+ (a charge of +1) when it combines with other atoms to make a compound.
Therefore, we say that sodium has an oxidation number of 1+.

6. Electric Charges
Most common charge

7. Chemical Bonding
The further apart two elements are on the periodic table, the more likely they form an ionic compound.
Covalent compounds form when elements have roughly equal tendency to accept electrons. Elements that are both nonmetals and therefore close together on the periodic table form covalent compounds.

8. Chemical Formulas
A chemical formula is a ratio of the atoms in a compound.
The charges in a chemical formula must add up to zero.

9. Determining a Chemical Formula
Determine the number of valence electrons each atom has.
2. Draw Lewis dot diagrams for each atom.
3. Fill empty electron spots – 8 is the magic number!

10. Chemical Formulas - Example
Lithium and Sulfur combine to form a compound.
How many valence electrons does each atom have?
What are the Lewis dot diagrams of each atom?
What are the charges of each element?
What is the chemical formula of this compound?

11. Chemical Formulas - Example
2. Aluminum and oxygen combine to form a compound.
How many valence electrons does each element have?
What are the Lewis dot diagrams of each atom?
What are the charges of each element?
What is the chemical formula of this compound?