1. Types of Chemical Bonds

2. IONIC COMPOUNDS AND IONIC BONDING
When solid sodium Na, and chlorine gas Cl2 react to form solid sodium chloride NaCl, a transfer of electrons occurs from the sodium atoms to the chlorine atoms to form sodium ions, Na+1 and chloride ions Cl-1 .
The sodium and chloride ions now have opposite electric charges and therefore attract each other
Ionic Bond  a chemical bond between oppositely charged ions.

3. IONIC COMPOUNDS AND IONIC BONDING
Ionic compounds result when a metal element reacts with a non-metal element to form positively charged and negatively charged ions that are held together by electrostatic attraction
This creates a crystal lattice structure.
NaCl is an example of a formula unit. A crystal formation only occurs when a large number of positive and negative ions come together.

4. MOLECULAR ELEMENTS AND COMPOUNDS, AND COVALENT BONDING
Covalent Bonding occurs when atoms share electrons. These shared electrons are called bonding electron pairs.
Typically are formed between atoms of non-metal elements.

5. LEWIS THEORY OF BONDING
Atoms and ions are stable if they have a full valence shell of electrons
Electrons are most stable when they are paired
Atoms form chemical bonds to achieved a full valence shell of electrons
A full valence shell of electrons may be achieved by an exchange of electrons between metal and non-metal atoms.
A full valence shell of electrons may be achieved by sharing of electrons between non-metals atoms
The sharing of electrons results in a covalent bond.

6. LEWIS STRUCTURES Lewis structure
a diagram that represents the arrangement of covalent electrons and bonds in a molecule or polyatomic ion.
Duet Rule
The observation that the complete outer shell of valence electrons when hydrogen and period 2 metals are involved.
Octet Rule
The observation that many atoms tend to form the most stable substances when they are surrounded by 8 electrons in their valence shells.

7. NUMBER OF BONDING SITES FOR CERTAIN ELEMENTS

8. STEPS FOR DRAWING LEWIS STRUCTURES
Ex. H2CO
1. Identify the central atom  highest bonding capacity. Then arrange atoms around it
Ex. C - has 4 bonding sites vs. O – has 2 bonding sites vs. H – has 1 bonding site
Since Carbon has 4 bonding sites it is the central atom
2. Add up the number of valence electrons available in an atom of each of the elements. This number represents the total number of electrons.
For Polyatomic Ions add 1 electron for a negative ion and remove 1 for a positive ion.
C = 4
O = 6
H = 2 x 1 Total is 12
 3. Place 1 pair of electrons between each adjacent pair of atoms. Every 2 dots represents a bonding electron pair that forms a single covalent bond.

9. STEPS FOR DRAWING LEWIS STRUCTURES
4. Place pairs of the remaining valence electrons as lone pairs on the surrounding atoms (not central). Follow octet rule.
5. Determine how many electrons are still available by subtracting the number of electrons you have used so far from the total number of valence electrons.
6. Place remaining electrons on the central atom in pairs.

10. Example Problem #1 Draw the Lewis structure and the structural formula for nitrate, NO2-

11. Example Problem #2 Draw the Lewis structure and the structural formula for NBr3

12.   Example Problem #3 Draw the Lewis structure and the structural formula for C2H4

13. Example Problem #4 Draw the Lewis structure and the structural formula for PO3-3

14. EXCEPTIONS TO THE OCTET RULE
When drawing Lewis structures for molecules, hydrogen atoms always obey the duet rule and carbon, nitrogen, oxygen and fluorine atoms obey the octet rule in all circumstances.
However there are exceptions to the octet rule.
The 1st exception applies to molecules with central atoms that are surrounded by fewer than 8 electrons.  underfilled octets
Ex. BF3
The 2nd exception applies to molecules with central atoms that are surrounded by more than 8 electrons.  overfilled octets
Ex. SF6

15.   Example Problem # 1 Draw the Lewis structure and the structural formula BeCl2

16. Example Problem #2 Draw the Lewis structure and the structural formula for PCl5

17.   Example Problem #3 Draw the Lewis structure and the structural formula for NCl4-

18. HOMEWORK
Answer Qs # 1 -6 Pg. 205