This document discusses quantum numbers and their role in describing electron orbitals and configurations. It covers the principal (n), azimuthal (l), and magnetic (ml) quantum numbers, as well as electron spin (ms). The document defines orbitals for the first five energy levels, discusses how electrons fill orbitals based on the Aufbau principle and Hund's rule, and notes exceptions like chromium and copper. It asks students to write electron configurations and diagrams for chlorine, osmium, and cesium.

8. • Principal Quantum Number, n
• Azimuthal Quantum Number, l
• Magnetic Quantum Number, ml

9. Exercise
• What are the similarities and differences
between the hydrogen atom 1s and 2s
orbitals?
• For n=4 what are the possible values of l and
m?
• give the values for n, l, m for
a. 2p
b. 5d
c. 5f

10. Main
Energy
Level
No. of
Sublevel
Identity of
Sublevels
No. of
Orbitals
(n2)
Max. No. of
Electrons
(2n2)
1 1 1s 1 2
2 2
2s
2p
1
3
2
6
3 3
3s
3p
3d
1
3
5
2
6
10
4 4
4s
4p
4d
4f
1
3
5
7
2
6
10
14

13. Electron Spin Quantum Number, m
• Two possible values are allowed
+ ½ and - ½
• Opposite directions

14. Can two electrons in an atom have the
same set of quantum numbers?

15. Pauli Exclusion Principle
• No two electrons in an atom can have the
same set of four quantum numbers, n, l, ml,
and ms.
• An orbital can hold a maximum of two
electrons and they must have opposite spins.

16. Electron Configuration
• The way in which electrons are distributed
among the various orbitals of an atom

17. Aufbau Principle
• Electrons occupy orbitals of lower energy first.

19. The relation between orbital filling and the periodic
table

20. The relation between orbital filling and the periodic
table

22. Hund’s Rule
• For degenerate orbitals, the lowest energy is
attained when the number of electrons with
the same spin is maximized.

23. Orbital Diagram

27. Anomalous Electron Configuration
Example:
Chromium
Copper

28. • Consequence of the closeness of the 3d and
4s orbital energies.
• Minor departures from the expected
• Not of great chemical significance

29. Seat work
Write the electron configuration and the
electron orbital diagram for the following
elements.
1. Cl
2. Os
3. Cs