1. Section 4.3—Electron Structure

2. The E-Config Hotel

3. The managers of this hotel are Aufbau, Hund , and Pauli.
Parking Garage
Shopping Center
Restaurant
The managers of this hotel are Aufbau, Hund , and Pauli.
You are an employee who works at the hotel. When placing guests in their rooms, you MUST follow the rules!

4. How the Electron Hotel Fillsp d
Restaurant
Shopping Center
Parking Garage
Rules:
“From the Bottom Up”: Rooms must be filled from the ground floor up (meaning you must fill the floors from lowest to highest). Fill the one room on the first floor before starting to put new guests on the second floor. Then fill the s room before the p rooms. Therefore, you must fill each room with two people before moving to the next floor.
“Singles First”: The manages of the hotel want to have the guests spread out as possible. For that reason, singles are placed in rooms before couples. This means that you place one person in each room, then go back and fill the rooms with the left over people. (**Remember ONLY TWO people per room!)
“Opposite Gender Only”: When two people are placed in a room, they must be of OPPOSITE genders. No men may room together and no women may room together. This is just an arbitrary rule the owners made!

5. Another Example f p s d Restaurant Shopping Center Parking Garage
If 8 people come to the hotel, where would you put them?
If 21 people come to the hotel, where would he put them?

6. f p d s
Restaurant
Shopping Center
Parking Garage
Remember! s BEFORE p, because lower in energy!
Remember! the further away from the ground (nucleus), the more energy!
Remember! Guests (electrons) want to be in the lowest energy level possible!

7. Where do electrons really live?

8. Electron Clouds
They don’t live in a hotel…They are in the area outside of the nucleus where the electrons reside.

9. Principal energy levels
Electron Clouds
Electron cloud
Electron Hotel
Which section of the hotel
Which floor
Which room
The electron cloud is made of energy levels (s,p,d,f)
Principal energy levels
Subshells
Energy levels are composed of subshells (1,2,3,4 …)
Orbitals
Subshells have orbitals.

10. Subshell versus Orbital
Subshell – A set of orbitals with equal energy
Orbital – Area of high probability of the electron being located.
Each orbital can hold 2 electrons

11. Electron Configuration

12. What are electron configurations?
They show the grouping and position of electrons in an atom.
The number and configuration of electrons determines how something glows…so it’s important to know “where the electrons live” for an atom!
Electron configurations use boxes for orbitals and arrows for electrons.

13. Energy and Subshells 6p 5d 4f 6s 5p 4d 5s 4p 3d 4s 3p 3s 2p
Subshells are filled from the lowest energy level to increasing energy levels. 2s
Energy
Does this look familiar? Electron Hotel! 1s

14. Aufbau Principle
The first of 3 rules that govern electron configurations
Aufbau Principle: Electrons fill subshells (and orbitals) so that the total energy of atom is the minimum 1
What does this mean?
Electrons must fill the lowest available subshells and orbitals before moving on to the next higher energy subshell/orbital.
Where did we see this “rule” in the Electron Hotel?

15. Hund’s Rule
Hund’s Rule: Place electrons in unoccupied orbitals of the same energy level before doubling up. 2
How does this work?
If you need to add 3 electrons to a p subshell, add 1 to each before beginning to double up.
Where did we see this “rule” in the Electron Hotel?

16. Pauli Exclusion Principle
Pauli Exclusion Principle: Two electrons that occupy the same orbital must have different spins. 3
“Spin” describes the angular momentum of the electron
“Spin” is designated with an up or down arrow.
How does this work?
If you need to add 4 electrons to a p subshell, you’ll need to double up. When you double up, make them opposite spins.
Where did we see this “rule” in the Electron Hotel?

17. Determining the Number of Electrons
Charge = # of protons – # of electrons
Atomic number = # of protons
Example:
How many electrons does Br-1 have?

18. Writing Electron Configurations
Aufbau Principle: Electrons fill subshells (and orbitals) so that the total energy of atom is the minimum 1 2
Hund’s Rule: Place electrons in unoccupied orbitals of the same energy level before doubling up.
Pauli Exclusion Principle: Two electrons that occupy the same orbital must have different spins. 3
Remember- determine the NUMBER of electrons before configuring!
Example:
Write the boxes & arrows configuration for Cl

19. Writing Electron Configurations
Aufbau Principle: Electrons fill subshells (and orbitals) so that the total energy of atom is the minimum 1 2
Hund’s Rule: Place electrons in unoccupied orbitals of the same energy level before doubling up.
Pauli Exclusion Principle: Two electrons that occupy the same orbital must have different spins. 3
Example:
Write the boxes & arrows configuration for Cl
No charge written  Charge is 0
Atomic number for Cl = 17 = # of protons
0 = 17 - electrons
Electrons = 17 4 13 12 11 14 15 8 17 16 10 9 1 2 5 3 6 7 1s 2s 2p 3s 3p

20. Spectroscopic Notation

21. Spectroscopic Notation
Shorthand way of showing electron configurations
The number of electrons in a subshell are shown as a superscript after the subshell designation 1s 2s 2p 3s 3p
1s2 2s2 2p6 3s2 3p5

22. Writing Spectroscopic Notation1
Determine the number of electrons to place 2
Follow Aufbau Principle for filling order
Fill in subshells until they reach their max (s = 2, p = 6, d = 10, f = 14). 3
The total of all the superscripts is equal to the number of electrons. 4
Example:
Write spectroscopic notation for S
No charge written  Charge is 0
Atomic number for S = 16 = # of protons
0 = 16 - electrons 1s 2s 2p 3s 3p 2 2 6 2 4
Electrons = 16 2 + 2 + 6 + 2 + 4 = 16

23. Noble Gas Configuration

24. Noble Gases & Noble Gas Notation
Noble Gas – Group 8 of the Periodic Table. They contain full valence shells.
Noble Gas Notation – Noble gas is used to represent the core (inner) electrons and only the valence shell is shown. Br
Spectroscopic 1s 2s 2p 3s 3p 2 6 4s 3d 10 4p 5
Noble gas
[Ar] 4s 2 3d 10 4p 5
The “[Ar]” represents the core electrons and only the valence electrons are shown

25. Which Noble Gas Do You Choose?
How do you know which noble gas to use to symbolize the core electrons?
Think: Price is Right.
How do you win on the Price is Right?
By getting as close as possible without going over.
Choose the noble gas that’s closest without going over!
Noble Gas
# of electrons He 2 Ne 10 Ar 18 Kr 36 Xe 54

26. Noble Gas Notation Example1
Determine the number of electrons to place 2
Determine which noble gas to use
Start where the noble gas left off and write spectroscopic notation for the valence electrons 3
Example:
Write noble gas notation for As

27. Noble Gas Notation Example1
Determine the number of electrons to place 2
Determine which noble gas to use
Start where the noble gas left off and write spectroscopic notation for the valence electrons 3
No charge written  Charge is 0
Example:
Write noble gas notation for As
Atomic number for As = 33 = # of protons
0 = 33 - electrons
[Ar] 4s 3d 4p 2 10 3
Electrons = 33 18 + 2 + 10 + 3 = 33
Closest noble gas: Ar (18)
Ar is full up through 3p