1. Warm-up
Write the noble gas configuration for the following neutral elements: K Se Ag U

2. Unit Three, Day Five Kimrey 21 September 2012
Chemistry
Unit Three, Day Five
Kimrey
21 September 2012

3. Valence Electrons
Valence electrons: the electrons in the highest energy level that are responsible for bonding and forming ions.
Write out the e- configuration and add up those that are in the highest energy level.

4. Example
How many valence electrons in Magnesium?

5. Practice
Determine the number of valence electrons for: C B Si

6. Lewis Dot Diagrams Visually expresses the number of valence electrons.
Write the symbol for the element
Draw the valence electrons around the symbol
- Start with one at the top, put the second one on the right, the third on the bottom, the fourth on the left, then start doubling up.

7. Example
Draw the Lewis dot structure for Oxygen.

8. More Practice
Write the Lewis dot diagrams for the following: Ca Si Fe

9. Remember…
Electron configuration describes the most likely location of the electron in an atom
It breaks the electron cloud into energy levels, sublevels, and spin direction

10. Orbital Filling Diagrams
Another expression of electron configuration.
Orbitals are shown as lines
Each line can hold up to two electrons
s has 1, p has 3, d has 5, and f has 7
Electrons are shown as arrows

11. Rules for Orbital Filling
Aufbau Principle-electrons will first occupy orbitals of the lowest energy level. Upper energy levels will not be filled until the lower levels are filled.
Pauli Exclusion Principle- no 2 electrons can have the same set of quantum numbers. Each orbital can hold a maximum of 2 electrons – the electrons MUST spin in opposite directions about their own axis
Hund’s Rule- orbitals of equal energy will contain a single electron throughout before doubling up

12. What?
What do these rules mean in PRACTICAL terms? When completing an orbital filling diagram (with arrows)
Start filling from the bottom.
Put one electron (arrow up) in each orbital before doubling up with a second electron(arrow down)
Do not fill a higher energy level until lower level(s) are completely filled

13. Steps Start by writing out the full electron configuration.
Translate the information from the electron configuration to the orbital filling diagram

14. Example
Draw the orbital filling diagram for Nitrogen. Cl

15. You Try
Draw the orbital filling diagrams for the following: P Al Na

16. What about ions??
Remember: An ion is when atoms gain or lose electrons.
They do this to become like noble gasses who have a full outer energy level.
Octet Rule: atoms need 8 valence electrons to be happy.
Exception is Helium because he only wants 2, note his highest energy level is still full!

17. Forming Ions
To predict the ion’s charge first determine the number of valence electrons.
The element can either gain or lose electrons…go with the smaller number.

18. Electron configuration of ions
Same as normal electron configuration but adjust for the gain or loss of electrons.
Note!!! It should look like a noble gasses e- configuration.

19. Example
What charge would the Magnesium ion have?
Sulfur ion?

20. You Try Determine the charges of the following ions. Oxygen Sodium
Aluminum