1. Subshells and Orbitals
Timberlake LecturePLUS 2000

2. Timberlake LecturePLUS 2000
Quantum Mechanics
Describes the arrangement of electrons in atoms in terms of:
Main or principal energy levels (n)
Energy subshells
Orbitals (space occupied within the atom)
Timberlake LecturePLUS 2000

3. Principal Energy Levels (n)
Contain electrons that are
Close in energy
Similar distance from nucleus
Have values of n = 1, 2, 3, 4, 5, 6…..
Maximum number of electrons = 2n2
n =1 2(1)2 = 2
n =2 2(2)2 =8
n=3
Timberlake LecturePLUS 2000

4. Energy Levels (Shells)
A group of electrons in an atom all having the same principal quantum number (n)
n = 1, 2, 3, …
The first shell (n = 1) is lowest in energy, 2nd level next and so on 1<2<3<4
The number of electron in each shell is limited to 2n2
n = 1 2n2 = 2
n = 2 2n2 = ____
Timberlake LecturePLUS 2000

5. Energy Levels for Electrons
Some possible electron transitions for the first three energy levels are shown below. The negative value means that the electron in the atom has a lower energy than a free electron
Energy Level Energy, E
n=3 ___________________ (-) x 1019 J
n=2 __________________ (-) x 1019 J
n=1 __________________ (-) x 1018 J
Timberlake LecturePLUS 2000

6. Timberlake LecturePLUS 2000
Learning Check S1
A. What energy change (J) takes place when an electron in a hydrogen atom moves from the first (n=1) to the second shell (n=2)?
B. What energy change (J) takes place when the electron moves from the third shell to the second shell?
Timberlake LecturePLUS 2000

7. Timberlake LecturePLUS 2000
Solution S1
A. What energy change takes place when an electron in a hydrogen atom moves from the first (n=1) to the second shell (n=2)?
1.634 x J of energy must be absorbed.
B. What energy change takes place when the electron moves from the third shell to the second shell?
( x 10-19J ) - ( x J) = x 1019J will be emitted as electron falls from a higher to a lower energy state
Timberlake LecturePLUS 2000

8. Timberlake LecturePLUS 2000
Subshells
Energy sublevels within energy level
All electrons in a subshell have the same energy
Designated s, p, d, f ..
Sublevel energy: s<p<d<f
Timberlake LecturePLUS 2000

9. Timberlake LecturePLUS 2000
Electron Locations
Main
Energy
Levels Sublevels
n=4 4s, 4p, 4d, 4f
n=3 3s, 3p, 3d
n=2 2s, 2p
n=1 1s
Timberlake LecturePLUS 2000

10. Timberlake LecturePLUS 2000
Sublevels in n = 1,2, 3 3d
n = 3 3p 3s 2p
n = 2 2s
n = 1 1s
Timberlake LecturePLUS 2000

11. Timberlake LecturePLUS 2000
Electrons Allowed
All electrons in the same sublevel have the same energy.
All 2s electrons have the same energy. All 2p electrons have the same energy which is slightly higher than the energy of the 2s electrons
s sublevel 2 electrons
p sublevel 6 electrons
d sublevel 10 electrons
f sublevel 14 electrons
Timberlake LecturePLUS 2000

12. Electron Configuration
List of subshells containing electrons
Written in order of increasing energy
Superscripts give the number of electrons
Example: Electron configuration of neon
number of electrons
1s2 2s2 2p6
main shell subshell
Timberlake LecturePLUS 2000

13. Timberlake LecturePLUS 2000
Order of Filling
Total energy of a subshell =
energy of the main shell + the subshell
The 4s energy < 3d energy
4p ___
3d ___ (finishes the n=3 shell)
4s ___ (starts the n=4 shell)
3p ___
3s ___
2p ___
2s ___
1s ___
Timberlake LecturePLUS 2000

14. Writing Electron Configurations
H 1s1
He 1s2
Li s2 2s1
C 1s2 2s2 2p2
S 1s2 2s2 2p6 3s2 3p4
Timberlake LecturePLUS 2000

15. Timberlake LecturePLUS 2000
Sublevel Blocks
s1 s p1 p2 p3 p4 p5 p6 1 2
d1 - d10 4 5 6
f1 - f14
Timberlake LecturePLUS 2000

16. Periodic Table and Electron Configuration
Find the element on the periodic table
Use the order of filling indicated across each period
Groups = s level
Groups 3-8 = p level
Transition = d level
Lantanides = f level
Timberlake LecturePLUS 2000

17. Timberlake LecturePLUS 2000
Learning Check S2
Indicate if each configuration is (1) correct or (2) incorrect for potassium. Give an explanation for selection of 1 or 2. Explain
why or why not?
A. 1s22s22p63s or 2
B s22s22p63s23p6 1 or 2
C. 1s22s22p63s23p64s1 1 or 2
D s22p83s or 2
E. 1s22s22p63s23p7 1 or 2
Timberlake LecturePLUS 2000

18. Timberlake LecturePLUS 2000
Solution E2
For phosphorus, indicate if each configuration is (1) correct or (2) incorrect. Explain why or why not.
A. 2, 2, 8, 5 2
B. 2, 8,
C. 2, 8, 5 1
D. 2, 6,
Timberlake LecturePLUS 2000

19. Learning Check S3
Using the periodic table, write the complete electronic configuration for each:
A. Cl
B. Sr
C. I

20. Timberlake LecturePLUS 2000
Solution S3
Using the periodic table, write the complete electronic configuration for each:
A. Cl
1s2 2s2 2p6 3s2 3p5
B. Sr
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
C. I
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5
Timberlake LecturePLUS 2000

21. Timberlake LecturePLUS 2000
Learning Check S4
A. The final two notations for Co are
1) 3p64s2
2) 4s24d7
3) 4s23d7
B. The final three notations for Sn are
1) 5s25p24d10
2) 5s24d105p2
3) 5s25d105p2
Timberlake LecturePLUS 2000

22. Timberlake LecturePLUS 2000
Solution S4
A. The final two notations for Co are
3) 4s2 3d7
B. The final three notations for Sn are
2) 5s2 4d10 5p2
Timberlake LecturePLUS 2000

23. Timberlake LecturePLUS 2000
Orbital
A 3 dimensional space around a nucleus in which electrons are most likely to be found
Shape represents electron density (not a path the electron follows)
Each orbital can hold up to 2 electrons.
Timberlake LecturePLUS 2000

24. s orbitals 3s 2s 1s

25. Three p Orbitals px pz py

26. p subshell contains p orbitals

27. d orbitals

28. Timberlake LecturePLUS 2000
Learning Check S5
A. Number of electrons in a p orbital
1) 1e 2) 1e or 2e 3) 3e
B. Number of orbitals in a p subshell
1) 1 2) 2 3) 3
C. Number of orbitals in 4d subshell
1) 1 2) 3 3) 5
D. Number of electrons (maximum) in a 3d subshell
1) 2e 2) 5e 3) 10e
Timberlake LecturePLUS 2000

29. Timberlake LecturePLUS 2000
Solution S5
A. Number of electrons in a p orbital
2) 1e or 2e
B. Number of orbitals in a p subshell
3) 3
C. Number of orbitals in 4d subshell
3) 5
D. Number of electrons in a 3d subshell
3) 10e
Timberlake LecturePLUS 2000