1. What are valence electrons?
Electrons in the outermost energy level.
They determine an element’s chemical properties.
They are involved in bonding.

2. Electrons in Energy Levels
1st energy level = 2 electrons
2nd energy level through the rest =
8 electrons
All energy levels seek a full valence so they are “stable”.

3. Groups or Families
These elements are closely related because they have the same number of valence electrons.
What does that mean?

4. Periods Periodic trends are established as you go across a row.
What happens to the elements as you go across the row?

5. Alkali Metals (Group 1)
These elements are highly reactive metals. WHY???
Lithium, Sodium, Potassium, Rubidium, Cesium, & Francium all have 1 valence e-.

6. Sodium (Na) Valence shell is not full.
It takes less energy to give away 1 electron than “steal” 7 more.

7. Alkaline Earth Metals (Group 2) Be, Mg, Ca, Sr, Ba, Ra
How many valence electrons do they have?
Are they still considered “reactive”? WHY?
Are they more/less reactive than Group 1?

8. Magnesium (Mg) What kind of an ion will it form? WHY???
It is easier (less energy) to give away 2 electrons than “steal” 6 from somewhere else.

9. Other Families Group 3 “Boron Family” Group 4 “Carbon Family”
Group 5 “Nitrogen Family”
Group 6 “Oxygen Family”
Group 7 “Halogens”
Group 8 “Noble Gases”

10. The Halogens (Group 7) Fluorine, Chlorine, Bromine, Iodine, Astatine.
Have 7 valence electrons (very reactive), they need 1 more to have a full valence!

11. The Noble Gases (Group 8)
Very stable and “unreactive” (inert).
All have 8 valence e- except for Helium.
Why is Helium still considered a noble gas?

12. What ion would Aluminum make?
How do you know?

14. Al +3

15. Ionization Cation has a POSITIVE net charge.
What kind of elements form Cations?
Group 1,2 & 3 do!
Anion has a NEGATIVE net charge.
What kind of elements form Anions?
Group 5,6 & 7 do!

16. How can we represent these types of molecules???
Electron Dot Diagram
A “model” chemists use represent the electron sharing in covalently bonded molecules.
Example: Hydrogen (H), has 1 valence electron. H·

17. The dots in an Electron Dot Diagram are placed in a specific order:
6 3
4 2
7 1
5 8 E

18. Try some on your own: Na, Mg, Al, C, N, and Cl