1. Electron Configurations
Section 3 Electron Configurations
Chapter 4
Electron Configurations
The arrangement of electrons in an atom is known as the atom’s electron configuration.
The lowest-energy arrangement of the electrons for each element is called the element’s ground- state electron configuration.

2. Relative Energies of Orbitals
Section 3 Electron Configurations
Chapter 4
Relative Energies of Orbitals

3. Rules Governing Electron Configurations
Section 3 Electron Configurations
Chapter 4
Rules Governing Electron Configurations
Aufbau principle- an electron occupies the lowest- energy orbital that can receive it.
Pauli exclusion principle- no two electrons with the same spin can occupy the same orbital

4. Rules Governing Electron Configurations, continued
Section 3 Electron Configurations
Chapter 4
Rules Governing Electron Configurations, continued
Hund’s rule- orbitals of equal energy are filled by one electron before any orbital is filled by a second electron.

5. Representing Electron Configurations, continued
Section 3 Electron Configurations
Chapter 4
Representing Electron Configurations, continued
Orbital Notation
The lines are labeled with the “principal quantum number” and sublevel letter. For example, the orbital notation for helium is written as follows: He
PQ# 1s
I’ll show you some examples
Try Aluminum, Chlorine, and Fluorine

6. Representing Electron Configurations, continued
Section 3 Electron Configurations
Chapter 4
Representing Electron Configurations, continued
Electron-Configuration Notation
Electron-configuration notation eliminates the lines and arrows of orbital notation.
The helium configuration is represented by 1s2.
Boron would be 1s22s22p1

7. Chapter 4 Boron would be 1s22s22p1...WHY?
Section 3 Electron Configurations
Chapter 4
Boron would be 1s22s22p1...WHY?

8. Section 3 Electron Configurations
Chapter 4
First we look the 1s2

9. Section 3 Electron Configurations
Chapter 4
Next we look the 2s2

10. These elements are in the s-block
Section 3 Electron Configurations
Chapter 4
These elements are in the s-block

11. Section 3 Electron Configurations
Chapter 4
Finally we look at 2p1

12. These elements are in the p-block
Section 3 Electron Configurations
Chapter 4
These elements are in the p-block

13. These elements are in the d-block
Section 3 Electron Configurations
Chapter 4
These elements are in the d-block

14. These elements are in the f-block
Section 3 Electron Configurations
Chapter 4
These elements are in the f-block

15. I want you to focus on s-block and p-block elements in this class
Visual Concepts
Chapter 4
A note about this class
The d-block elements are not going to play much of a role in our study of chemistry. You’ll learn more in college.
The f-block elements will almost never be mentioned unless we’re studying nuclear chemistry.
I want you to focus on s-block and p-block elements in this class

16. Representing Electron Configurations, continued
Section 3 Electron Configurations
Chapter 4
Representing Electron Configurations, continued
Sample Problem A
The electron configuration of neon is 1s22s22p6. How many electrons are present in an atom of neon? What is the atomic number for neon? Write the orbital notation for neon.

17. Elements of the Second Period, continued
Section 3 Electron Configurations
Chapter 4
Elements of the Second Period, continued
The highest-occupied energy level is the electron- containing main energy level with the highest principal quantum number.
The electrons in the highest-occupied energy level will be called valence electrons.
Inner-shell electrons are electrons in completely filled orbitals.

18. Chapter 4 Knowledge check
Section 3 Electron Configurations
Chapter 4
Knowledge check
Use the definitions from the previous slide to determine the number of valence electrons present in each of the following elements:
Hydrogen
Oxygen
Sulfur
Xenon

19. Writing Electron Configurations
Section 3 Electron Configurations
Chapter 4
Writing Electron Configurations

20. Elements of the Third Period
Section 3 Electron Configurations
Chapter 4
Elements of the Third Period
After the outer octet is filled in neon, the next electron enters the s sublevel in the n = 3 main energy level.
Noble-Gas Notation
The Group 18 elements (helium, neon, argon, krypton, xenon, and radon) are called the noble gases.
A noble-gas configuration refers to an outer main energy level occupied, in most cases, by eight electrons.

21. Orbital Notation for Three Noble Gases
Section 3 Electron Configurations
Chapter 4
Orbital Notation for Three Noble Gases

22. Section 3 Electron Configurations
Chapter 4
Elements of the Fourth Period Warning: Don’t read this, it will make you dumber!
The period begins by filling the 4s orbital, the empty orbital of lowest energy.
With the 4s sublevel filled, the 4p and 3d sublevels are the next available vacant orbitals.
The 3d sublevel is lower in energy than the 4p sublevel. Therefore, the five 3d orbitals are next to be filled.

23. Just look at the periodic table!!!
Section 3 Electron Configurations
Chapter 4
Just look at the periodic table!!!

24. Orbital Notation for Argon and Potassium
Section 3 Electron Configurations
Chapter 4
Orbital Notation for Argon and Potassium

25. Chapter 4 Sample Problem B
Section 3 Electron Configurations
Chapter 4
Sample Problem B
a. Write both the complete electron-configuration notation and the noble-gas notation for iron, Fe.
b. How many electron-containing orbitals are in an atom of iron? How many of these orbitals are completely filled? How many unpaired electrons are there in an atom of iron? In which sublevel are the unpaired electrons located?

26. Just look at the periodic table!!!
Section 3 Electron Configurations
Chapter 4
Just look at the periodic table!!!

27. Chapter 4 Sample Problem C
Section 3 Electron Configurations
Chapter 4
Sample Problem C
a. Write both the complete electron-configuration notation and the noble-gas notation for a rubidium atom.
Identify the elements in the second, third, and fourth periods that have the same number of valence electrons as rubidium.
They all have similar chemical properties…

28. Sample Problem C Solution
Section 3 Electron Configurations
Chapter 4
Sample Problem C Solution
a. 1s22s22p63s23p63d104s24p65s1, [Kr]5s1
b. Rubidium has one electron in its highest energy level (the fifth). The elements with the same outermost configuration are,
in the second period, lithium, Li;
in the third period, sodium, Na;
and in the fourth period, potassium, K.

29. Section 3 Electron Configurations
Chapter 4
Now you know…
1) Why all element of the same family have similar properties
2) why the periodic table is shaped the way it is
3) enough to understand the next lesson

30. Break into your groups, I want…
Section 3 Electron Configurations
Chapter 4
Break into your groups, I want…
1) Orbital notation for carbon, sodium, and iron.
2) Electron configuration notation for titanium, calcium, and bromine
3) Noble gas notation for calcium, bromine, iodine, lead, plutonium, radon, francium and lithium.
Isn’t noble gas notation easy?

31. Break into your groups, I want…
Section 3 Electron Configurations
Chapter 4
Break into your groups, I want…
You’ve had a lot of lecture today, but I never covered this objective.
Explain the particle/wave nature of electrons and how that lead to the quantum mechanical model of the atom.
You don’t need to know this, but if you understand this, you’re wise beyond your years and peers.