1. Introduction to Chemistry Bohr Models and Lewis Dot Structures

2. Atoms
Basic unit of matter
Consists of: Electrons, Protons, & Neutrons

3. Atoms Review Consists of: Electrons, Protons, & Neutrons
Electrons: particles orbiting around nucleus with a negative charge
Protons: particles in the nucleus with positive charge
Neutrons: particles in the nucleus with no charge

4. Element a pure chemical substance consisting of one type of atom
Atomic Number= Number of Protons or Electrons
Symbol
Name
Atomic Mass= Number of Protons + Number of Neutrons

5. Periodic Table of Elements
VIII +1 II
III IV V VI
VII +2 +3
+/-4 -3 -2 -1
= element charges
= Valence Electrons

6. Periods and Groups
Periods go from left to right
Groups go up and down

7. Bohr Models Proposed by Niels Bohr in 1915
Electrons orbit the nucleus in orbits that have a set size and energy.
The energy of the orbit is related to its size.
The lowest energy is found in the smallest orbit.

8. Energy Levels
When two atoms approach each other their nucleus do not touch
Only electrons are involved in Chemical Reactions

9. Bohr Diagrams Find out which period (row) your element is in.
Elements in the 1st period have one energy level.
Elements in the 2nd period have two energy levels, and so on.

10. Bohr Models RULE Show just electrons with energy levels
1st level holds 2
2nd holds 8
3rd holds 18 but is stable at 8
2-8-8 RULE!!
Must fill an energy level to capacity before moving to the next energy level

11. Bohr Diagrams Try the following elements on your own: H He O Al Ne KP: N:

12. Valence Electrons
Electrons that are found on the outer most energy level. This determines the elements chemical properties

13. Lewis Dot Structures Named after Gilbert Newton Lewis
Show the bonding between atoms of a molecule, and the lone pairs of electrons that may exist in the molecule
Show only valence electrons (outer energy level)

14. Lewis Dot Structures and Groups
Find out which group (columns) your element is in.
Elements in the 1st group have one valence electron.
Elements in the 2nd group have two valence electrons, and so on.

15. Lewis Dot
Try the following elements on your own: H He O Al Ne K

16. More Practice
                                                                           

17. Answers