1. The Quantum Mechanical Picture of the Atom
The allowed energy states of atoms and molecules can be described by sets of numbers called quantum numbers
n  m ms

2. Quantum Numbers  - the angular momentum quantum number
n - the principal quantum number
n = 1, 2, 3, 4, “shells”
 - the angular momentum quantum number
 = 0, 1, 2, 3, … , n – 1 “subshells”
 = s, p, d, f,
m - the magnetic quantum number
m = –, – + 1, … ,  – 1, 
ms - the spin quantum number
ms = –½, +½

3. Quantum Numbers and Orbitals
Define the energy of the electron 
Defines the shape of the orbital
Orbital
The volume around the nucleus where the electron appears 90-95% of the time
The Pauli principle
No two electrons in an atom may have identical sets of four quantum numbers

4. s orbital ( = 0)
There is only one s orbital per n level

5. p orbital ( = 1) There are 3 p orbitals per n level
They are named px , py , and pz

6. d orbital ( = 2)
There are 5 d orbitals per n level

7. f orbital ( = 3)
There are 7 f orbitals per n level

8. Order of Orbital Energy

9. Building Atoms
Build the nucleus by adding the required # of protons and neutrons according to the atomic # and mass # of the atom
Fill energy levels (orbitals) with the required # of electrons starting from the lowest available energy level and following Pauli and Hund rules (this is called Aufbau principle)

10. Building Atoms - Period 1
n  m ms H He

11. Building Atoms - Period 2
n  m ms Li Be

12. Building Atoms - Period 2
n  m ms B C

13. Hund’s Rule
Electrons occupy all the orbitals of a given subshell (with the same ) singly before pairing begins. These unpaired electrons have parallel spins (the same sign of ms).
n  m ms C

14. Building Atoms - Period 2F Ne

15. Building Atoms - Period 3Na P Mg S Al Cl Si Ar

16. Building Atoms - Period 4K Ca
Sc – 4p or 3d ?