1. Quantum Numbers

2. Quantum Numbers energy levels, size Pathway of travel
Describes the arrangement of electrons in atoms in terms of:
energy levels, size
Pathway of travel
Direction of rotation

3. Principal Quantum number (n)
Contain electrons that are similar in energy and distance from nucleus
Low energy electrons are closest to the nucleus
Identify by numbers 1, 2, 3, 4, 5, 6…..
The first shell (1) is lowest in energy, 2nd level next and so on 1<2<3<4

4. Number of Electrons
Maximum number of electrons in any electron energy level = 2n2
n =1 2(1)2 = 2
n =2 2(2)2 = 8
n =3 2(3)2 = 18

5. Orbital Quantum number
Indicates the pathway of travel
Electrons move in different paths due to their negative charge.
Designated s, p, d, f ..
Sublevel energy: s<p<d<f

6. Magnetic Quantum number
Orientation of path
Direction of movement with respect to the nucleus

7. S orbitals 1 s orbital for every energy level Spherical shaped
Each s orbital can hold 2 electrons
Called the s s s etc.. orbitals.

8. P orbitals 3 different directions 3 identical shapes
Each can hold 2 electrons

9. P Orbitals put together

10. D orbitals Higher in energy than s or p due to advanced shape
5 shapes, 4 are identical

11. F orbitals
More complex still
Have seven different shapes

12. F orbitals
More complex still

13. Spin Quantum number Describes rotation of electron in an orbital
Either clockwise (+1/2) or
Counter clockwise (-1/2)

14. Summary Seven energy levels (n=1,2,3,4…) Four pathways (s,p,d,f)
Orientations: s=1, p=3, d=5, f=7
Two spins in each orbital
Maximum electrons are: s=2, p=6, d=10, f=14

15. Summary Max # electrons/orbital # of shapes/orbitals
Starts at energy level s 1 2 1 p 3 6 2 d 5 10 3 7 14 4 f

16. By Energy Level First Energy Level only s orbital only 2 electrons 1s2
Second Energy Level
s and p orbitals are available
2 in s, 6 in p
2s22p6
8 total electrons

17. By Energy Level Third energy level s, p, and d orbitals
2 in s, 6 in p, and 10 in d
3s23p63d10
18 total electrons
Fourth energy level
s,p,d, and f orbitals
2 in s, 6 in p, 10 in d, ahd 14 in f
4s24p64d104f14
32 total electrons

18. By Energy Level
Any more than the fourth and not all the orbitals will fill up.
You simply run out of electrons
The orbitals do not fill up in a neat order.
The energy levels overlap
Lowest energy fill first.

19. Electron Locations Main Energy Levels Sublevels n=4 4s, 4p, 4d, 4f

20. Sublevels in n = 1,2, 3 3d
n = 3 3p 3s 2p
n = 2 2s
n = 1 1s

21. Electrons Allowed
All electrons in the same sublevel have the same energy.
All 2s electrons have the same energy. All 2p electrons, the same energy which is slightly higher than that of the 2s electrons
s sublevel 2 electrons
p sublevel 6 electrons
d sublevel 10 electrons
f sublevel 14 electrons

22. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p 3s 2p

23. Electron Configurations
List of subshells containing electrons
Written in order of increasing energy
Superscripts give the number of electrons

24. Electron Configuration
Example: Neon
number of electrons
1s2 2s2 2p6
main shell subshell

25. Electron Configurations
The way electrons are arranged in atoms.
Aufbau principle- electrons enter the lowest energy first.
This causes difficulties because of the overlap of orbitals of different energies.
Pauli Exclusion Principle- at most 2 electrons per orbital - different spins

26. Electron Configuration
Hund’s Rule- When electrons occupy orbitals of equal energy they don’t pair up until they have to .
Let’s determine the electron configuration for Phosporus
Need to account for 15 electrons

27. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
The first to electrons go into the 1s orbital
Notice the opposite spins
only 13 more

28. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
The next electrons go into the 2s orbital
only 11 more

29. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
The next electrons go into the 2p orbital
only 5 more

30. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p
The next electrons go into the 3s orbital
only 3 more

31. Increasing energy 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s
The last three electrons go into the 3p orbitals.
They each go into seperate shapes
3 upaired electrons
1s22s22p63s23p3

32. The easy way to remember
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2
2 electrons

33. Fill from the bottom up following the arrows
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2
4 electrons

34. Fill from the bottom up following the arrows
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2 2p6 3s2
12 electrons

35. Fill from the bottom up following the arrows
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2 2p6 3s2 3p6 4s2
20 electrons

36. Fill from the bottom up following the arrows
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
38 electrons

37. Fill from the bottom up following the arrows
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2
56 electrons

38. Fill from the bottom up following the arrows
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2
88 electrons

39. Fill from the bottom up following the arrows
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 6f
7s 7p 7d 7f
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6
108 electrons

40. Writing Electron Configurations
H 1s1
He 1s2
Li s2 2s1
C 1s2 2s2 2p2
S 1s2 2s2 2p6 3s2 3p4

41. Periodic Table and Electron Configuration
Find element on the periodic table
Use the order of filling indicated across each period
Groups = ns level
Groups 3-8 = np level
Transition = (n-1)d level
Lanthanides = (n-2)f level

42. Exceptions to Electron Configuration

43. Orbitals fill in order Lowest energy to higher energy.
Adding electrons can change the energy of the orbital.
Half filled orbitals have a lower energy.
Makes them more stable.
Changes the filling order

44. Write these electron configurations
Titanium - 22 electrons
1s22s22p63s23p64s23d2
Vanadium - 23 electrons 1s22s22p63s23p64s23d3
Chromium - 24 electrons
1s22s22p63s23p64s23d4 is expected
But this is wrong!!

45. Chromium is actually 1s22s22p63s23p64s13d5 Why?
This gives us two half filled orbitals.
Slightly lower in energy.
The same principal applies to copper.
Write the Cu configuration now

46. Copper’s electron configuration
Copper has 29 electrons so we expect
1s22s22p63s23p64s23d9
But the actual configuration is
1s22s22p63s23p64s13d10
This gives one filled orbital and one half filled orbital.
Remember these exceptions

47. Orbital Notation
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.

48. 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
1) 2e 2) 5e 3) 10e

49. 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

50. The Periodic Law
All the elements in a group have the same electron configuration in their outermost shells
Example: Group 2
Be 2, 2
Mg 2, 8, 2
Ca 2, 2, 8, 2

51. Learning Check EA5
Specify if each pair has chemical properties that are similar (1) or not (2):
A. Cl and Br
B and
C and
D. P and S
E. O and S

52. Solution EA5
Specify if each pair has chem. properties that are similar (1) or not similar (2):
A. Cl and Br 1
B and
C and
D. P and S 2
E. O and S 1

53. 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
A. 1s22s22p63s or 2
B s22s22p63s23p6 1 or 2
C. 1s22s22p63s23p64s1 1 or 2
D s22p83s or 2
E. 1s22s22p63s23p7 1 or 2

54. 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,

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

56. 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

57. 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

58. 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