1. Chem
Take out “Electron Address” to be stamped if you did not get it stamped last class
Take out a Periodic Table (you’ll need one for today)
Unit 7 Quiz/Quest this Fri 3/2!
Waves, Energy, Electrons

2. Aufbau Principle
Under normal conditions, each electron occupies the lowest energy orbital available.

3. Pauli Exclusion Principle
Every electron spins; it can spin in one of two directions.
An arrow pointing up (↑) indicates one direction.
An arrow pointing down (↓) indicates the other direction.
The Pauli exclusion principle states that a maximum of two electrons can occupy an orbital space, but only if they have opposing spins. OR
RIGHT
WRONG

4. Hund’s Rule WRONG RIGHT
To minimize repulsion between electrons, Hund’s rule says that we put one electron in each orbital of the same energy before we add the second.
p subshell
WRONG
RIGHT
Room mate rule

5. Magnesium Mg 3p 3s
1s22s22p63s2 2p 2s 1s

6. Silicon Si 3p 3s
1s22s22p63s23p2 2p 2s 1s

7. Sulfur S 3p 3s
1s22s22p63s23p4 2p 2s 1s

8. Electron Configuration: 3 parts
# electrons in orbital
Energy Level
Type of orbital

10. 2 2 4

11. O 2 2 4 8

12. Electron Configuration
Fill out the long form electron configuration first.
We will do the Noble Gas Abbreviation and Valence Electron part after.

13. Valence Electrons
The electrons in the outermost shell or highest energy level
Valence electrons = total number of electrons in the highest s and p orbitals (must be of the same energy level)!

14. Noble Gases: Group 18 Have octet=full valence (outermost) shell
All elements want to be a noble gas (so freaking bad). In other words, all elements want to have a full valence shell
Remember: “8 IS GREAT!”
Exception: helium: it only has 2 valence electrons

15. Electron Configurations can get very long!
Abbreviated Electron Configuration for Be:
Find the closest noble gas that comes before it
[He] eliminates the need to write “1s2”
[He]
2s2
2 valence electrons

16. [Ne] eliminates the need to write “1s22s22p6”
Abbreviated Electron Configuration for Na:
Find the closest noble gas that comes before it
[Ne] eliminates the need to write “1s22s22p6”
[Ne]
3s1
1 valence electron

17. Obtaining a Noble Gas Electron Configuration
Elements can lose or gain electrons in order to get a noble gas’ electron configuration
Metals tend to lose electrons to obtain a noble gas electron configuration
Nonmetals tend to gain electrons to obtain a noble gas electron configuratoin

18. 10
(8+2)
gain
1s2
2s2
2p6 8