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. Bohr’s Model
Bohr’s atomic model of electrons in orbits with specific levels of energy was only partly correct.
The idea of electron shells is not quite sufficient to explain the behaviour of atoms.
We need to add the concept of orbitals and quantum numbers for elements with multiple electrons.

3. Orbitals In Bohr’s model, electrons existed within main energy levels
Now  electrons still exist in main energy levels BUT within each level there are sublevels called orbitals.

4. Principal Quantum Number, n
The principal quantum number represents the shell or main energy level.
Main energy levels are given values: n = 1, 2, 3, 4…
The shell or main energy level indicates the the size of an orbital (or how far away the electron is from the nucleus)  the higher the number, the larger the orbital (or the farther the electron).
As n increases, so does energy.

5. Principal Quantum Number describes the size!!
Relative Sizes 1s and 2s
Principal Quantum Number describes the size!!
1s s
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 334

6. Secondary Quantum Number, l
The secondary quantum number divides the shells or main energy levels up into smaller groups of subshells called orbitals it also describes the shape of orbital.

7. Secondary Quantum Number, l
Subshells are given letter codes: s, p, d, f, g…
There is one s-shaped orbital within
each main energy level.
There are three p-shaped orbitals within main energy levels 2+. Each of the p-shaped orbitals have a different orientation in space.

8. There are five d-shaped orbitals within main energy levels 3+
There are five d-shaped orbitals within main energy levels 3+. Each of the d-shaped orbitals have a different orientation in space.
There are seven f-shaped orbitals within main energy levels 4+. Each of the f-shaped orbitals have a different orientation in space.

9. Secondary Quantum Number, l
Within a given shell, the subshells (orbitals) are in order of increasing energy:
4s < 4p < 4d < 4f (increasing energy)

10. Magnetic Quantum Number, ml
Splits the subshells into individual orbitals. Describes orientation in space, thus gives 3D information.

11. Maximum Number of Electrons In Each Sublevel
Sublevel Number of Orbitals of Electrons s p d f
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 146

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

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

14. Spin Magnetic Number, ms
Indicates the orientation of the two electrons in each orbital.
Values are +1/2 or –1/2

15. - Spin Quantum Number, ms North South S N
The electron behaves as if it were spinning about an axis through its center.
This electron spin generates a magnetic field, the direction of which depends
on the direction of the spin.
Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 208

16. Atomic Orbitals

17. Principal Energy Levels 1 and 2

18. s, p, and d-orbitals
Kelter, Carr, Scott, , Chemistry: A World of Choices 1999, page 82

19. Electron Configurations
Objectives:
To state the energy sublevels within a given energy level.
To state the maximum number of electrons that occupy a given energy level and sublevel.
To list the order of sublevels according to increasing energy.
To write the predicted electron configurations for selected elements.

20. How do we fill orbitals?
Atom is most stable when electrons have the lowest possible energy.
That is when they occupy the lowest possible energy orbitals available.

21. 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. NO TWO ELECTRONS CAN HAVE THE SAME FOUR
QUANTUM NUMBERS!!
Hund’s Rule:Within a given set of orbitals, one electron will go in each
orbital before pairing-up begins.

22. Energy Level Diagram of a Many-Electron Atom
6s p d f 32
5s p d 18
4s p d
Arbitrary
Energy Scale 18
3s p 8
2s p 8 1s 2
NUCLEUS
O’Connor, Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 177

23. Sublevels 4f 4d 4p 4s n = 4 3d 3p 3s n = 3 Energy 2p 2s n = 2 1s n = 1

24. Electron Configurations and the Periodic Table
Electron Configurations and the Periodic Table

25. H He Li C N Al Ar F Fe La Energy Level Diagram Bohr Model
6s p d f
Bohr Model
5s p d
4s p d
Arbitrary Energy Scale
3s p N
2s p 1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F Fe La
CLICK ON ELEMENT TO FILL IN CHARTS

26. Hydrogen H = 1s1 H He Li C N Al Ar F Fe La Energy Level Diagram
Hydrogen
6s p d f
Bohr Model
5s p d
4s p d
Arbitrary Energy Scale
3s p N
2s p 1s
Electron Configuration
NUCLEUS
H = 1s1
H He Li C N Al Ar F Fe La
CLICK ON ELEMENT TO FILL IN CHARTS

27. Helium He = 1s2 H He Li C N Al Ar F Fe La Energy Level Diagram
Helium
6s p d f
Bohr Model
5s p d
4s p d
Arbitrary Energy Scale
3s p N
2s p 1s
Electron Configuration
NUCLEUS
He = 1s2
H He Li C N Al Ar F Fe La
CLICK ON ELEMENT TO FILL IN CHARTS

28. Lithium Li = 1s22s1 H He Li C N Al Ar F Fe La Energy Level Diagram
Lithium
6s p d f
Bohr Model
5s p d
4s p d
Arbitrary Energy Scale
3s p N
2s p 1s
Electron Configuration
NUCLEUS
Li = 1s22s1
H He Li C N Al Ar F Fe La
CLICK ON ELEMENT TO FILL IN CHARTS

29. Carbon C = 1s22s22p2 H He Li C N Al Ar F Fe La Energy Level Diagram
Carbon
6s p d f
Bohr Model
5s p d
4s p d
Arbitrary Energy Scale
3s p N
2s p 1s
Electron Configuration
NUCLEUS
C = 1s22s22p2
H He Li C N Al Ar F Fe La
CLICK ON ELEMENT TO FILL IN CHARTS

30. Nitrogen N = 1s22s22p3 H He Li C N Al Ar F Fe La Energy Level Diagram
Nitrogen
6s p d f
Bohr Model
5s p d
4s p d
Arbitrary Energy Scale
3s p N
Hund’s Rule “maximum
number of unpaired orbitals”.
2s p 1s
Electron Configuration
NUCLEUS
N = 1s22s22p3
H He Li C N Al Ar F Fe La
CLICK ON ELEMENT TO FILL IN CHARTS

31. Electron Configurations
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