1. Electron Dot Diagrams

2. Electrons are found in various energy levels (orbits)
The electrons in the outer energy levels are the ones which usually participate in chemical reactions
The outer electrons allow us to explain the combining powers of atoms
They are called valence electrons

3. Example: Chlorine
How many electrons are in the 1st and 2nd orbit combined? 10
They are considered the inner electrons

4. How many electrons are in the 3rd (outer) energy level?
Chlorine
How many electrons are in the 3rd (outer) energy level? 7

5. The electron dot diagram
Since the valence electrons of an atom are so important in determining its chemical properties, chemists have developed a special symbol:
The electron dot diagram

6. How to draw a Electron Dot Symbol
Write the chemical symbol
This symbol represent the whole atom: the nucleus and inner electrons
The outer or valence electrons are then drawn as dots surrounding the chemical symbol

7. Example: Chlorine Cl

8. Bonding Atoms who gain or lose electrons are referred to as ions
If an atom loses electrons it becomes positively charged (+)  cation
If an atom gains electrons it becomes negatively charged (-)  anion

9. Positively charged Ions:
Common Ions
Positively charged Ions:
Na+  lost 1 electron
K+  lost 1 electron
Mg2+  lost 2 electrons

10. Li+ Al3+ Example What is the charge for Lithium?
What is the charge for Aluminum?
Al3+

11. Negatively Charged Ions
F-  gained 1 electron
S2-  gained 2 electron
Cl-  gained 1 electron

12. N3- Br- Example What is the charge for Nitrogen?
What is the charge for Bromine?
Br-

13. Positively charged ions bind to negatively charged ions
Positively charged ions are metals
Negatively charged ions are non-metals

14. We can use an electron dot diagram to represent the transfer of electrons from the metal to the non-metal
Let’s do an example!!!

15. Draw the Electron Dot Diagram for Sodium and Chlorine (separately)
Na Cl
[Na]+ [ Cl ]-

16. Homework Complete Worksheets: Keeping an ION that Electron
Electron Dot Shells