1. Quantum Mechanical Model
Main Concept:
The currently accepted best model of the atom is based on the quantum mechanical (QM) model.

2. Evidence for Quantum Mechanical Model
Electrons & QM Model
Subshells & Orbitals s p d f
Evidence for Quantum Mechanical Model
What we expect without subshells
What subshells explain
Valence Electrons and Electron Configurations

3. - Coulomb’s law describes the energy interaction between protons and electrons
- Electrons do not follow specific orbits 
- orbital: regions of space where electrons are found

4. - Electrons have an intrinsic property called spin that results in atoms having a magnetic moment.  
- An orbital can hold two electrons at most and electrons must have opposite spin (Pauli Exclusion Principle)

5. Electron Configurations
s subshell has 1 orbital and holds two electrons
p subshell has 3 orbitals and holds six electrons
d subshell has 5 orbitals and holds ten electrons
f subshell has 7 orbitals and holds fourteen electrons
Order of subshells:
1s 2s 2p 3s 3p 4s 3d 4p
5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p

6. Electron Configurations
Hund’s Rule: a single electron must first occupy each orbital within a subshell before orbital is doubly occupied and single electrons in orbitals must all have same spin
Aufbau Principle: electrons fill lowest energy level first before filling higher levels

7. Electron Configurations
Longhand Configuration Examples:
for Si: 1s2 2s2 2p6 3s2 3p2
for In: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p1
Shorthand/Noble Gas Configuration Examples:
for Si: [Ne] 3s2 3p2
for In: [Kr] 5s2 4d10 5p1

8. 7 6 5 4 3 C N O F Ne B Li Be 2 H He 1

9. Group 1A:
H: 1s1
Li: 1s2 2s1
Na: 1s2 2s2 2p6 3s1
K: 1s2 2s2 2p6 3s2 3p6 4s1

10. Group 2A:
Be: 1s2 2s2
Mg: 1s2 2s2 2p6 3s2
Ca: 1s2 2s2 2p6 3s2 3p6 4s2

11. Group 3A:
B: 1s2 2s2 2p1
Al: 1s2 2s2 2p6 3s2 3p1
Ga: 1s2 2s2 2p6 3s2 3p1 4s2 3d10 4p1
Ga: 1s2 2s2 2p6 3s2 3p1 3d10 4s2 4p1

12. Group 4A:
C: 1s2 2s2 2p2
Si: 1s2 2s2 2p6 3s2 3p2
Ge: 1s2 2s2 2p6 3s2 3p1 4s2 3d10 4p2
Ge: 1s2 2s2 2p6 3s2 3p1 3d10 4s2 4p2

13. Group 5A:
N: 1s2 2s2 2p3
P: 1s2 2s2 2p6 3s2 3p3
As: 1s2 2s2 2p6 3s2 3p1 4s2 3d10 4p3
As: 1s2 2s2 2p6 3s2 3p1 3d10 4s2 4p3

14. Group 6A:
O: 1s2 2s2 2p4
S: 1s2 2s2 2p6 3s2 3p4
Se: 1s2 2s2 2p6 3s2 3p1 4s2 3d10 4p4
Se: 1s2 2s2 2p6 3s2 3p1 3d10 4s2 4p4

15. Group 7A:
F: 1s2 2s2 2p5
Cl: 1s2 2s2 2p6 3s2 3p5
Br: 1s2 2s2 2p6 3s2 3p1 4s2 3d10 4p5
Br: 1s2 2s2 2p6 3s2 3p1 3d10 4s2 4p5

16. Group 8A:
He: 1s2
Ne: 1s2 2s2 2p6
Ar: 1s2 2s2 2p6 3s2 3p6
Kr: 1s2 2s2 2p6 3s2 3p1 4s2 3d10 4p6
Kr: 1s2 2s2 2p6 3s2 3p1 3d10 4s2 4p6

17. - The quantum mechanical (QM) model addresses problems classical shell model
- QM model consistent with atomic electronic structures that correspond with the periodic table

18. Problems with the Bohr Model
- Not all of the spectra
could be correctly
predicted for larger atoms
and couldn’t explain certain
spectra
- Contradicted Heisenberg’s Uncertainty Principle; it assumed knowledge of both location and momentum

19. What does the QM model address?
- The dual nature of the electron (as a particle and a wave)
- Correctly predicts spectra
- Allows for probability waves in agreement with Heisenberg’s Uncertainty Principle
- Consistent with periodic models, data, and trends

21. Question:
What explanation could possibly be given for why IE’s in periods 2 and 3 increase but also decrease?

25. - The QM model can be appropriately solved using computers and serves as the basis for software that calculates the structure and reactivity of molecules. 

26. s p p s p p d d d s d d d p p s f f f f