1. Chapter 2 The Material World
Molecules
Chapter 2
The Material World

2. Bonds

3. Octet Rule An atom is chemically stable if it has a full outer shell
For most elements this means 8 electrons in its outermost shell
An atoms that has fewer than 8 electrons tends to combine with another atom or atoms to fill the outermost shell.
Exceptions:
H, He, Li, Be and B, desire 1 orbital only with 2 electrons in this shell.

4. Example of an ionic bond:2+ 2- Mg S

5. What do atoms do to become chemically stable?
Gain electrons (non metals)
Lose electrons (metals)
Share electrons 2+ 2- Mg S

6. OR What is a chemical bond? It’s the “Glue” holding atoms together
Attraction between opposite charges due to transfer of electrons
(ionic bond)
Pair of shared electrons
(covalent bond) OR

7. Ionic Bonds
Bonds formed by the transfer of valence electrons between atoms
→ Forming ions

8. Covalent Bonds
Bonds formed by the sharing of valence electrons between atoms

9. Review: Lewis Dot Notation

10. Lewis Dot Notation
Shows only the electrons in the last orbit since these are the electrons involved in chemical bonding.
Examples:
Na Br

11. Lewis Dot Notation – Ion Formation
The ion an element is most likely to form is dependent on the number of valence electrons
Remember the octet rule: each atom wants to have a complete outer ring

12. Lewis Dot Notation – Ion Formation
Example
What is the ion that Aluminum forms?
13 p+ Al 3+ Al Al
10 e- 3+
Dropped to lower level

13. Element
Lewis Dot Diagram
Neutral
Chemical Ion
Hydrogen
Antimony
Barium
Oxygen

14. Element
Lewis Dot Diagram
Neutral
Chemical Ion
Beryllium
Polonium
Cesium
Nitrogen