1. Bonding

2. Types of Chemical Bonds
Ionic Bonds
Covalent Bonds
Transfer of electrons from the metal to the non-metal, creating two oppositely charged ions.
Sharing of electrons between two non-metals.
The bonding pair of electrons are found in the region of space between the two nuclei.
Electrostatic force of attraction between ions.

3. Lewis Theory for Ionic Compounds
Atoms and ions are stable if they have a full octet.
Electrons are most stable when they are paired.
Use arrows to represent the transfer of electrons.
The final structure will contain ions.

4. Lewis Theory for Covalent Compounds
Atoms are stable if they have a full octet.
Electrons are most stable when they are paired.
Non-metals will share electrons to obtain a full valence shell.
A molecules structural formula can be visualized but constructing a Lewis Structure.

5. Lewis Structures
Simple covalent compounds such as CH4 may be done by pairing electrons from different atoms. The pairing is shown with circles.
More complex covalent compounds and polyatomic ions should be drawn using an alternative method.

6. The Process For Drawing Complex LD Diagrams
Determine the total number of valence electrons available.
Draw the diagram placing the central atom in the middle and the surrounding atoms around it.
Put a pair of electrons between the atoms for bonds.
Complete the octets for all external atoms.
If there are electrons left over, place around the central atom.
If the central atom does not have a full octet, use electrons from the external atoms to create a multiple bond between the central atom and an exterior atom.

8. Non-Octet Compounds
Some compounds will contain central atoms that do not follow the octet rule.
The four possibilities for non-octet compounds are:
Where more than 4 atoms are bonded to the central atom such as PCl5.
A noble gas is participating in bonding such as XeF4.
Where the central atom has less than 8 valence electrons such as BH3.
Where molecules contain an odd number of nonbonding electrons such as NO.

9. Resonance Structures
For some molecules, there are multiple ways of placing the electrons between the atoms.
Structures that differ only in the arrangement of the electrons are called RESONANCE STRUCTURES.
Resonance structures are indicated using a double headed arrow.

10. Coordinate Covalent Bonds
A coordinate covalent bond results when both electrons in the bond are donated from the same atom.
To determine if a bond is coordinate covalent, compare the number of non-bonding electrons around an atom to the number of valence electrons the atom has.

11. Homework
Read Section 4.1
Page 200 #1,2
Page 204 #1,2