1. Quantum Numbers

2. What are they?
Characterization of the orbital that an electron occupies
Describes the following:
distance from the nucleus
shape
position with respect to the 3 dimensional axis
direction of spin of the electron

3. What are orbitals? Area to that an electron pair can reside in
There are four main “shapes” for orbitals
Orbitals can be found in shells which are main energy levels
aka the rings or orbits around a nucleus

4. Principal Quantum Number
Abbreviated as n
Represents the distance of an electron from the nucleus & the main energy level of the electron.
n is numerically represented by positive integers.

5. n2 = # of orbitals in a shell 2 n2 = # of electrons in a shell Shell #
Each orbital can house an electron pair!
Shell #
#e- 1 2 8 3 18 4 32 5 50

6. Angular Momentum Abbreviated by l
Describes the shape of an orbital by using a number and letter designation.
Determined by all values between n-1…0 l
Letter s 1 p 2 d 3 f

7. Shapes s orbital is spherical p orbital looks like a dumbell
d orbitals look like 2 dumbells
f orbitals look like flowers

11. Magnetic Quantum Number
Abbreviated by ml
Represents the 3 dimensional orientation of an orbital
Assumes all values –l…0…+l

12. If n=1
Then l=0
So ml=0
Think of spinning a basketball on your finger…does it really change where it is in 3D??

13. For a p orbital… n=2 l=1 ml= -1, 0, +1
The p orbital can exist in different planes in 3D

14. Spin Quantum Number Abbreviated by ms Uses +1/2 or -1/2
Indicates the direction of spin of an electron
Electrons in the same orbital have opposite spins!

15. A Picture of the Spinning Electron

16. How do we determine QN’s?
Must use 3 main rules and determine the electron configuration!

17. Aufbau Principle
Electrons must enter the lowest shell and orbital first!

18. Hund’s Rule
orbitals of equal energy will be occupied by one electron before a second one may enter
No one can have seconds until everyone has gone through once!!

19. Pauli’s Exclusion Principle
No 2 electrons in the same orbital can have the same 4 Quantum Numbers!!
Don’t worry because each will have an opposite spin!!