1. Chemical Bonding

2. Chemical Bond
The forces that hold groups of atoms together and make them function as a unit
Bonding involves only the valence electrons
Electrons are transferred or shared to give each atom a noble gas configuration (stable octet)
This is known as the octet rule
There are 2 types of bonds:
Ionic: Transfer of electrons from a metal and to a nonmetal
Covalent: Sharing of electrons between 2 nonmetals

3. Lewis Diagrams
Valence electrons involved in bonding can be represented by Lewis dot diagrams
A chemical symbol represents the nucleus and the core electrons (not involved in bonding).
Dots around the symbol represent valence electrons.

4. Drawing Lewis Diagrams
Write the element symbol.
Draw dots, one for each valence electron
Dots should be spread over 4 sides
It does not matter what side the dots are placed, but do not start to pair dots until there is one on each side
The number of valence electrons is equal to the group number (for groups 1-3, 14-18), with one exception. Which element is it? Cl

5. Lewis diagrams for the first 20 elements

6. Ionic Bonding Metals Nonmetals Electron donors
Donate their valence electrons to become a positive ion (cation)
Nonmetals
Electron acceptors
Accept valence electrons to become a negative ion (anion)

7. Ionic Bonding

8. Ionic Bonding
The two oppositely charged ions are attracted to each other by a force called an ionic bond

9. Properties of Ionic Compounds
Structure:
Crystalline solids
Melting point:
Generally high
Boiling Point:
Electrical Conductivity:
Excellent conductors, molten and aqueous
Solubility in water:
Generally soluble

10. NaCl Crystal Lattice Ionic compounds form solids at SATP.
Ionic compounds organize in a characteristic crystal lattice of alternating positive and negative ions.
All lattices are arranged so that each ion has the greatest possible number of oppositely charged ions close by, while keeping similarly charged ions as far away as possible

11. Representing Ionic Compounds Lewis Diagrams
Formation of sodium chloride: Cl
· ·
Na+ [ ] Cl
· · Na +

12. Lewis Structures for Ionic CompoundsBa • O •• •• O Ba 2+ 2-
Ba and O
BaO Mg • Cl •• •• Cl Mg 2+ - 2
Mg and Cl
Binary ionic compounds.
Note the types of arrows used to move electrons – fishhooks for single e-.
Write the Lewis symbol for each atom Determine how many e- each atom must gain or lose.
Use multiples of one or both ions to balance the number of electrons.
MgCl2

13. Practice Problems
p. 68 #1,4
p. 71 #1-5
p. 73 #8-13