1. Section 4.3—Electron Structure

2. The Electron Hotel

3. The story of the Electron Hotel
Parking Garage
Shopping Center
Restaurant
A man built an hotel for electrons with a restaurant next door.
But he was making so much money that he decided to add on with some more rooms and a parking garage.
He still had high demand and decided to add on some more rooms and a shopping center.
He used the last space he could to put some rooms above the shopping center.

4. How the Electron Hotel Fills
Restaurant
Shopping Center
Parking Garage
This man had some very strange ideas about how to run his hotel. He insisted four things:
The lowest possible must be used first (actually it was the fire inspector that insisted on this one)
There can only be one person in a room until all rooms at that level have someone
No more than 2 people to a room
When two people are in a room, they must be of opposite sex
If 8 people come to the hotel, where would he put them?

5. Another Example Shopping Center Parking Garage Restaurant
This man had some very strange ideas about how to run his hotel. He insisted four things:
The lowest possible must be used first (actually it was the fire inspector that insisted on this one)
There can only be one person in a room until all rooms at that level have someone
No more than 2 people to a room
When two people are in a room, they must be of opposite sex
If 21 people come to the hotel, where would he put them?

6. You Try Shopping Center Parking Garage Restaurant
This man had some very strange ideas about how to run his hotel. He insisted four things:
The lowest possible must be used first (actually it was the fire inspector that insisted on this one)
There can only be one person in a room until all rooms at that level have someone
No more than 2 people to a room
When two people are in a room, they must be of opposite sex
If 42 people come to the hotel, where would he put them?

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
Principal energy levels
Subshells
Energy levels are composed of subshells
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. Number of equal energy orbitals Total number of electrons possible
Types of Subshells
Subshell
Begins in energy level
Number of equal energy orbitals
Total number of electrons possible s 1 1 2 p 2 3 6
Energy increases d 3 5 10 f 4 7 14

12. Electron Configuration

13. 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.

14. 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

15. 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?

16. 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?

17. 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?

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

19. Determining the Number of Electrons
Charge = # of protons – # of electrons
Atomic number = # of protons
Example:
How many electrons does Br-1 have?
Charge = -1
Atomic number for Br = 35 = # of protons
-1 = 35 - electrons
Electrons = 36

20. 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

21. 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

22. Spectroscopic Notation

23. 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

24. 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

25. Noble Gas Configuration

26. 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

27. 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

28. 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

29. 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