1. Quantum Numbers Activity

2. Warm-Up Write the electron configuration for Uranium
Now, write the abbreviated electron configuration for Europium

3. Helping Us Understand Electron Configurations
Quantum Numbers
Helping Us Understand Electron Configurations

4. Electron Configurations
The distribution of electrons into the various energy shells and subshells in an atom in its ground state is called its electron configuration.
Each energy shell and subshell has a maximum number of electrons it can hold.
s = 2, p = 6, d = 10, f = 14.
Based on the number of orbitals in the subshell.
We place electrons in the energy shells and subshells in order of energy, from low energy up.
Aufbau principle.
Tro's "Introductory Chemistry", Chapter 9

5. Quantum Numbers Like giving each electron its own address
Quantum numbers tell us properties of the atomic orbitals, and electrons, in an atom
Like giving each electron its own address
We understand this idea from electron configurations
An orbital is a 3-D region of an atom where there is a high probability of finding electrons (NOT an actual ring & NOT like the planetary orbitals)

6. Principal Quantum Number Angular Momentum Quantum Number
Magnetic Quantum Number
Spin Quantum Number

7. Textbook
You will need a textbook to look up information about the quantum numbers.

8. Know for each Quantum # Definition Symbol The allowed values
An example
A visual representation of the quantum number

9. Review Quantum Numbers as a Class
Discussion of the 4 types of quantum numbers and there properties

10. Quantum Number Review Notes

11. Quantum Numbers
Used to describe various properties of the orbitals in an electron configuration
Each electron is assigned a set of four quantum numbers which, in order, are n, l, ml , and ms
Like giving each electron its own address

12. Principle quantum number
Definition: indicates the main energy level occupied by the electron
Symbol: n
Values: (written as integers) 1,2,3,4,5,6,7

13. Angular Momentum Quantum Numbers
Definition: indicates the shape of the orbital
Symbol: l
Values:
0 = s
1 = p
2 = d
3 = f
For a specific energy level, the number of orbital shapes available is equal to n -1

14. Magnetic Quantum Numbers
Definition: represents the orientation of an orbital around the nucleus
Symbol: ml
Values: for a p-orbital -1, 0 , 1

15. Spin Quantum Numbers
Definition: represents the spin states of electrons in an orbital
Symbol: ms
Values: +1/2, - ½

17. Can an e- be described by the following set of quantum numbers?
n=2, l=1, ml= -1
All quantum numbers are allowed values

18. Can an e- be described by the following set of quantum numbers?
n=1, l=1, ml= +1
Not possible.
The value of l must be less than the value
of n.

19. Can an e- be described by the following set of quantum numbers?
n=7, l=3, ml= +3
All the quantum numbers are allowed
values.

20. Can an e- be described by the following set of quantum numbers?
n=3, l=1, ml=-3
Not possible.
The value of ml must be in the range
-l to +l

21. Replace the ? Mark with an appropriate quantum number.
n=3, l=1, ml=?
n=4, l=?, ml=-2
n=?, l=3, ml=?

22. Can an e- be described by the following set of quantum numbers?
n=2, l=1, ml=-2
n=3, l=2, ml=+2
n=4, l=3, ml=+3
n=5, l=2, ml=+3

23. An easier yet longer way to write electron configurations
Orbital Diagrams
An easier yet longer way to write electron configurations

24. 6d 7s 5f 6p 5d 6s 4f 5p 4d 5s 4p 3d Energy 4s 3p 3s 2p 2s 1s
Tro's "Introductory Chemistry", Chapter 9

25. Filling an Orbital with Electrons
Each orbital may have a maximum of 2 electrons.
Pauli Exclusion principle.
Electrons spin on an axis.
Generating their own magnetic field.
When two electrons are in the same orbital, they must have opposite spins.
So their magnetic fields will cancel.
Tro's "Introductory Chemistry", Chapter 9

26. Tro's "Introductory Chemistry", Chapter 9
Orbital Diagrams
We often represent an orbital as a square and the electrons in that orbital as arrows.
The direction of the arrow represents the spin of the electron.
Unoccupied
orbital
Orbital with
1 electron
Orbital with
2 electrons
Tro's "Introductory Chemistry", Chapter 9

27. Order of Subshell Filling in Ground State Electron Configurations
Start by drawing a diagram
putting each energy shell on
a row and listing the subshells
(s, p, d, f) for that shell in
order of energy (left to right). 1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d 7s
Next, draw arrows through
the diagonals, looping back
to the next diagonal
each time.
Tro's "Introductory Chemistry", Chapter 9

28. Filling the Orbitals in a Subshell with Electrons
Energy shells fill from lowest energy to highest.
Subshells fill from lowest energy to highest.
s → p → d → f
Orbitals that are in the same subshell have the same energy.
When filling orbitals that have the same energy, place one electron in each before completing pairs.
Hund’s rule.
Tro's "Introductory Chemistry", Chapter 9

29. Electron Configuration of Atoms in their Ground State
The electron configuration is a listing of the subshells in order of filling with the number of electrons in that subshell written as a superscript.
Kr = 36 electrons = 1s22s22p63s23p64s23d104p6
A short-hand way of writing an electron configuration is to use the symbol of the previous noble gas in [] to represent all the inner electrons, then just write the last set.
Rb = 37 electrons = 1s22s22p63s23p64s23d104p65s1 = [Kr]5s1
Tro's "Introductory Chemistry", Chapter 9

30. Electron Configurations
Tro's "Introductory Chemistry", Chapter 9