1. Electron Configuration
Chapter 4
Quantum numbers,
describe the orbitals in which electrons can be found.

2. Bohr was wrong!!
Electrons spend time around the nucleus but NOT in nice neat circular orbits.

3. Where are the electrons?
We cannot know exactly where the electrons are.
We can only know with some degree of certainty where it is.
Quantum numbers describe where the electron may be found.
Quantum numbers are the electrons “address”.

4. Dual nature of light and matter
Energy travels in packets of energy, sort of like steps.
When an electron is excited to a higher energy level, it emits light when it returns to its original orbit.
Law of Conservation of Energy.

6. principle quantum number (n)
Describes the size of the orbital.
Referred to as the energy level.

7. The angular quantum number (l)
(l) describes the shape of the orbital.
Spherical , s, (l = 0)
Polar, p. (l = 1)
Cloverleaf ,d, (l = 2)
They can even take on more complex shapes as the value of the angular quantum number becomes larger.

9. magnetic quantum number
Magnetic quantum number (m)
Describes the orientation in space of a particular orbital. X,Y, Z axis
Named magnetic quantum number because the effect of different orientations of orbitals was first observed in the presence of a magnetic field.

10. Spin Each orbital shape may hold two electrons.
These two electrons have opposite spins.
Designated as ½ & - ½

11. Da Rules
The principle Quantum Number is an integer greater than or equal to 1.
The angular quantum number (l) can be any integer between 0 and n - 1. If n = 3, for example, l can be either 0, 1, or 2.
The magnetic quantum number (m) can be any integer between -l and +l. If l = 2, m can be either -2, -1, 0, +1, or +2.
Spin is + ½ & - ½

12. Shells and Subshells of Orbitals
Orbitals that have the same value of the principle quantum number form a shell. Orbitals within a shell are divided into subshells that have the same value of the angular quantum number. Chemists describe the shell and subshell in which an orbital belongs with a two-character code such as 2p or 4f. The first character indicates the shell (n = 2 or n = 4).

13. Shells and Subshells of Orbitals
The second character identifies the subshell. By convention, the following lowercase letters are used to indicate different subshells. s:
l = 0 p:
l = 1 d:
l = 2 f:
l = 3

15. The d orbitals

16. Electron Configuration
H: 1s1
A hydrogen atom has only one electron.
The lowest energy orbital is the 1s orbital.
This is indicated by writing a superscript "1" after the symbol for the orbital.

17. Aufbau principle
Each electron is added to the lowest energy orbital available.
Up to two electrons may be added to each orbital.
He: 1s2
Li: 1s2 2s1
Be: 1s2 2s2
B: 1s2 2s2 2p1
C: ????????
C: 1s2 2s2 2p2

18. But:
After all not all the orbitals are filled in Energy Level order!!

20. Hund's rules can be summarized as follows.
One electron is added to each of the degenerate orbitals in a subshell before two electrons are added to any orbital in the subshell.
Electrons are added to a subshell with the same value of the spin quantum number until each orbital in the subshell has at least one electron.
Filling the Bus!

21. Pauli Exclusion Principle
No two electron in an atom may have the same set of quantum numbers.
This is Pauli. Don’t Mess with Pauli!