1. Chemical Bonding

2. Why do atoms bond?
What makes an atom stable? Full outer energy level with 8 valence electrons (highest orbitals are s & p)
Atoms bond (react with each other) to obtain stable, noble gas electron configurations.
How do atoms acquire the noble gas configuration? By losing, gaining, or sharing of valence electrons.

3. What is a chemical bond?
That is the question you should be able to answer at the end of the notes over this unit 

4. Ionic Bonds

5. Formation of an ionic bond
1. An ionic bond involves a metallic cation and a non-metallic
anion.
2. The number of electrons lost must equal the number of
electrons gained.
Chemical Bond - a force that hold 2 atoms together
Ionic Bond - an attraction between a cation and an anion (between a + and -)
- metals are always written first in the formula
  Oxidation # - # of the transferred electrons from an atom to another atom. It is the same as a charge.

6. Electron Dot Structures
Example 1
Combination of Ca and F
valence e- for Ca = ____ valence e- for F = ____
Electron Dot Structures
Ca F
Oxidation # Ca: ___ Oxidation # F: ___
Number of Ca needed: ___ Number of F needed: ____

7. Example 1 cont’d

8. Electron Dot Structures
Example 2
Combination of Sodium and Nitrogen
valence e- for Na = ____ valence e- for N = ____
Electron Dot Structures
Na N
Oxidation # Na: ___ Oxidation # N: ___
Number of Na needed: ___ Number of N needed: ____

9. help sheet Group #: 1A 2A 3A 4A 5A 6A 7A 8A
Valence e-:
Oxidation #: /

10. Covalent Bonds

11. But what about 2 atoms that BOTH need to GAIN electrons?
Review
Ionic Bond – Electrostatic attraction between positive ion of metal (cation) and negative nonmetallic ion (anion).
But what about 2 atoms that BOTH need to GAIN electrons?

12. Covalent Bonds
Covalent Bond – Chemical bond resulting from the sharing of valence electrons (bond between two non-metals) 1. Most covalent bonds are between nonmetals (exceptions Be and B) 2. Generally occurs when elements are relatively close to each other on the PT. 3. The shared e- are considered part of the complete outer energy levels of both atoms involved. Two atoms share an e- pair simultaneously.

13. A molecule is formed when 2 or more nonmetallic. atoms bond covalently
A molecule is formed when 2 or more nonmetallic atoms bond covalently. All covalent compounds are also called molecular compounds.
EX. H2O water
Cl2 chlorine gas
O2 oxygen gas
CO2 carbon dioxide gas
CH4 methane gas
NH3 ammonia

14. Bonding pair (shared pair) – Pair of valence electrons
Bonding pair (shared pair) – Pair of valence electrons shared between 2 atoms. (Represented by a pair of dots or a line in the Lewis (electron dot) structure)

15. Lone Pairs
Lone pair – unshared pair of electrons.

16. Diatomic molecules
BrINClHOF
Ex: H2 Ex: F2

17. Rules for # of bonds H - 1 Be - 2 B – 3
Group 4A - 4 Group 5A- 3 Group 6A- 2
Group 7A- 1

18. Examples
a. HCl b. H2O
c. NH d. CH4

19. Types of covalent bonds
A. Single Covalent Bond – 2 atoms share one pair of electrons (2 e-) Ex: HCl
B. Multiple Bonds
1. Double Covalent Bond – 2 atoms share two pairs of electrons. (4 e-) Ex: O2
2. Triple Covalent Bond – 2 atoms share three pairs of electrons. (6 e-) Ex: N2

20. Strength of covalent bonds
TYPE OF BOND
BOND LENGTH
BOND STRENGTH
BOND DISSOCIATION ENERGY
Single Bond
Longest
Weakest
Lowest
Double Bond
Shorter
Stronger
Higher
Triple Bond
Shortest
Strongest
Highest

21. Molecular Shapes

22. VSEPR model (Valence Shell Electron Pair Repulsion theory)
1. This model is based on the arrangement that minimizes the
repulsion of shared and unshared pairs of electrons around
the central atom.
2. Bond angle – The angle formed by any 2 terminal atoms and
3. Lone pairs are NOT shared between 2 nuclei and occupy a
slightly larger orbital space than shared e-. (Since lone pairs
occupy more space, they push shared pairs together
slightly.)