1. Electron Configuration & Orbitals
1s22s22p63s23p64s23d104p65s24d104p65s24d105p66s24f145d106p6…
Objectives:
To describe the quantum mechanical model of the atom.
To describe the relative sizes and shapes of s and p orbitals.

2. Orbital Shapes
Bohr model shows electrons travelling a 2-dimensional circular path
Quantum Mechanical Model shows electrons in a 3-dimensional region of space

3. 1s 2s Relative Sizes 1s and 2s
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 334

4. p-Orbitals
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 335

5. d-orbitals
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 336

6. Shapes of s, p, and d-Orbitals

7. Atomic Orbitals

9. s, p, and d-orbitals A s orbitals: Hold 2 electrons (outer orbitals of
Groups 1 and 2) B
p orbitals:
Each of 3 pairs of
lobes holds 2 electrons
= 6 electrons
(outer orbitals of
Groups 13 to 18) C
d orbitals:
Each of 5 sets of
lobes holds 2 electrons
= 10 electrons
(found in elements
with atomic no. of 21
and higher)
Kelter, Carr, Scott, , Chemistry: A World of Choices 1999, page 82

10. Say Goodbye to the Bohr Model…

11. …and hello to the Modern Atomic Model

12. Electron Configuration
Use a symbol that contains 3 pieces of information
n = the number of the principal quantum shell
l = the letter the designates the orbital type
superscript number = designate the number of electrons in that subshell
Ex: 2p4
Means 4 electrons in a p subshell with a principal quantum number of 2

13. Aufbau Process
1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p
Increasing energy

14. Filling Rules for Electron Orbitals
Aufbau Principle: Electrons are added one at a time to the lowest
energy orbitals available until all the electrons of the atom
have been accounted for.
Pauli Exclusion Principle: An orbital can hold a maximum of two electrons.
To occupy the same orbital, two electrons must spin in opposite
directions.
Hund’s Rule: Electrons occupy equal-energy orbitals so that a maximum
number of unpaired electrons results.
*Aufbau is German for “building up”

15. Orbitals Being Filled Groups 1 8 2 1s 1 3 4 5 6 7 1s 2s 2 2p 3 3s 3p 1s 2s 2 2p 3 3s 3p
Periods 4s 3d 4p 4 4d 5p 5 5s La 5d 6p 6 6s Ac 6d 7 7s 4f
Lanthanide series 5f
Actinide series

16. Aligning Electron Configurations With the Periodic Table

17. Pauli Exclusion Principle
The Pauli Exclusion Principle says that electrons in the same orbital must have opposite spins. 1s

18. Hund’s Rule
Hund’s Rule says that electrons in the same energy level and sublevel must fill each orbital with one electron before pairing them up. 1s 2s 2p 3s 3p

19. Box Orbital Diagrams Hydrogen = 1 proton = 1 electron
Write the Electron Configuration for:
Hydrogen = 1 proton = 1 electron 1s 2s 2p 3s 3p
Helium = 2 protons = 2 electrons 1s 2s 2p 3s 3p
Lithium = 3 protons = 3 electrons 1s 2s 2p 3s 3p

20. Box Diagrams Boron = 5 proton = 5 electron
Write the Electron Configuration for:
Boron = 5 proton = 5 electron
Box Diagrams 1s 2s 2p 3s 3p
Nitrogen = 7 protons = 7 electrons 1s 2s 2p 3s 3p
Chlorine = 17 protons = 17 electrons 1s 2s 2p 3s 3p

21. Electron Configurations
Orbital Filling
Element 1s s px 2py 2pz s Configuration
Electron H He Li C N O F Ne Na
1s1
1s2
1s22s1
1s22s22p2
1s22s22p3
1s22s22p4
1s22s22p5
1s22s22p6
1s22s22p63s1