section 4.3—electron structure. the e-config hotel
TRANSCRIPT
Section 4.3—Electron Structure
The E-Config Hotel
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!
Parking GarageShopping Center
sp d
f
Restaurant
How the Electron Hotel Fills
Rules:1. “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.
2. “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!)
3. “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!
Parking GarageShopping Center
f
s p d
RestaurantParking Garage
Another Example
If 8 people come to the hotel, where would you put them?
If 21 people come to the hotel, where would he put them?
Shopping Center
sp
df
RestaurantParking Garage
Shopping Center
s p df
• 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!
Where do electrons really live?
Electron Clouds
They don’t live in a hotel…They are in the area outside of the nucleus where the electrons reside.
Electron Clouds
Electron cloud
Principal energy levels
Subshells
Orbitals
The electron cloud is made of energy levels (s,p,d,f)
Energy levels are composed of subshells (1,2,3,4 …)
Subshells have orbitals.
Electron Hotel
Which section of the hotel
Which floor
Which room
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
Electron Configuration
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.
Energy and Subshells
1s
2s
3s
4s
5s
2p
3p
4p
5p
3d
4d
6s
6p5d
4f
Ene
rgy
Subshells are filled from the lowest energy level to increasing energy levels.
Does this look familiar? Electron Hotel!
Aufbau Principle
Aufbau Principle: Electrons fill subshells (and orbitals) so that the total energy of atom is the minimum
1
The first of 3 rules that govern electron configurations
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?
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?
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?
Determining the Number of Electrons
Charge = # of protons – # of electrons
Atomic number = # of protons
Example:How many electrons does Br-1
have?
Writing Electron Configurations
Aufbau Principle: Electrons fill subshells (and orbitals) so that the total energy of atom is the minimum1
Pauli Exclusion Principle: Two electrons that occupy the same orbital must have different spins.3
Hund’s Rule: Place electrons in unoccupied orbitals of the same energy level before doubling up.2
Example:Write the boxes & arrows
configuration for Cl
Remember- determine the NUMBER of electrons before configuring!
Writing Electron Configurations
Aufbau Principle: Electrons fill subshells (and orbitals) so that the total energy of atom is the minimum1
0 = 17 - electrons
No charge written Charge is 0
Atomic number for Cl = 17 = # of protons
Electrons = 17
Pauli Exclusion Principle: Two electrons that occupy the same orbital must have different spins.3
Hund’s Rule: Place electrons in unoccupied orbitals of the same energy level before doubling up.2
1s 2s 2p 3s 3p
4231567910111213141516178
Example:Write the boxes & arrows
configuration for Cl
Spectroscopic Notation
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
Writing Spectroscopic Notation
Determine the number of electrons to place1
Fill in subshells until they reach their max (s = 2, p = 6, d = 10, f = 14).3
Follow Aufbau Principle for filling order2
The total of all the superscripts is equal to the number of electrons.4
0 = 16 - electrons
No charge written Charge is 0
Atomic number for S = 16 = # of protons
Electrons = 161s 2s 2p 3s 3p2 2 6 2 4
2 2 6 2 4+ + + + = 16
Example:Write
spectroscopic notation for
S
Noble Gas Configuration
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.
1s 2s 2p 3s 3p2 2 6 2 6 4s 2 3d 10 4p 5
4s 2 3d 10 4p 5[Ar]
Br
Spectroscopic
Noble gas
The “[Ar]” represents the core electrons and only the valence electrons are shown
How do you know which noble gas to use to symbolize the core electrons?
Which Noble Gas Do You Choose?
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
Ne
Ar
Kr
Xe
2
10
18
36
54
Noble Gas Notation Example
Determine the number of electrons to place1
Start where the noble gas left off and write spectroscopic notation for the valence electrons3
Determine which noble gas to use2
Example:Write noble gas notation
for As
+
Noble Gas Notation Example
Determine the number of electrons to place1
Start where the noble gas left off and write spectroscopic notation for the valence electrons3
Determine which noble gas to use2
0 = 33 - electrons
No charge written Charge is 0
Atomic number for As = 33 = # of protons
Electrons = 33
[Ar] 4s 3d 4p2 10 3
18 2 10 3+ + = 33Closest noble gas: Ar (18)
Ar is full up through 3p
Example:Write noble gas notation
for As