1. Ch. 6 Chemical Bonding
A Chemical Bond occurs when valence electrons are lost, gained, transferred or shared between two or more atoms.

2. The Octet Rule Atoms tend to gain, lose, or share electrons
until they have eight valence electrons.
This is called a “Stable Octet.”

3. Why Do Atoms form a Bond? To form a state of lower potential energy.
Bonded atoms require less energy
To become more stable.
A Stable Octet of 8 electrons resembles the Nobel Gases.

4. The Three types of Bonds
Ionic Bond – Transfer of electrons from a cation to an anion.

5. The Three types of Bonds
Covalent Bond Sharing of electrons so that all atoms involved maintain a Stable octet.

6. Three types of Bonds
Metallic Bond Cations attracted to other Cations by a sea of electrons surrounding all of the positive ions.
Sea of electrons

7. Identifying the Bond
When Metals bond to Non-Metals they will form an Ionic Bond
When Non-Metals bond to other Non-Metals they will form a Covalent Bond
When Metals bond to other Metals they will form a Metallic Bond

8. Lewis Dot Diagrams
Lewis symbols show the valence electrons as dots arranged around the atomic symbol.
hydrogen:
sodium:
chlorine: H Na Cl
· ·

9. Using Lewis Dot Diagrams for Ionic compounds and Covalent molecules
Formation of sodium chloride: Cl
· ·
Na+ [ ] Cl
· · Na +
Formation of hydrogen chloride: Cl
· · Cl
· · H H +
When filling up valence shells make sure all non-metals finish with a stable octet. If possible all elements should finish with an octet.

10. Ex. NaCl and MgO not “ClNa” or “OMG”
Basic Formula Writing
When writing a formula the most metallic element is written first.(leftmost on the P.table)
Ex. NaCl and MgO not “ClNa” or “OMG”
Subscripts are to be used to represent the number of elements or ions needed to make all species maintain a octet.
Ex. H2O or AlBr3
(A subscript of 1 is understood and is not written.)

11. Bond Determination H + F Ca + Cl Al + O * Cu + N K + P N + Br As + S
Using e-dot diagrams determine the formulas for the following.
Metal to Non-Metal  Ionic
Non-Metal to Non-Metal  Covalent
H + F
Ca + Cl
Al + O
* Cu + N
K + P
N + Br
As + S
Ionic Covalent HF
CaCl2
Al2O3
Cu3N or Cu3N2
K3P
NBr3
As2S3
When writing the formula of a compound or molecule the more metallic element is always written 1st ( furthest to the left)

12. Determining Formulas The Criss-Cross Method
A short cut to formula writing can be accomplished using the oxidation or charge of ions to determine the chemical formulas of compounds.
Examples
Na+1 + O-2 
Ca+2 + P-3 
C+4 + O-2 
Na2O
Ca3P2
C2O4  reduced to CO2