Transcript Chemistry You Need to Know

Section 4.3—Electron
Addresses
The Electron Hotel-a relatively reasonable analogy.
The story of the Electron Hotel
Shopping Center
Parking Garage
Restaurant
A man built a 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.
How the Electron Hotel Fills
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 floor must be used first
• There can only be one person in a room until all the rooms at that level
have one person.
• 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?
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
• 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?
Where are electrons really located?
In Electron Clouds!
Electron Hotel
Electron
cloud
Which section
of the hotel
Principal
energy levels
The electron cloud is
made of energy levels
Which floor
Subshells
Energy levels are
composed of subshells
Which room
Orbitals
Subshells have orbitals.
Subshell versus Orbital
Subshell – A set of orbitals with equal
energy (A set of rooms on the same floor)
Orbital – Area of high probability of the
electron being located.
Each orbital can hold 2 electrons
Energy increases
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
d
3
5
10
f
4
7
14
Some people do find good health ---- a quick way to remember subshell order!
What are electron configurations?
Think of it as an energy address for
your electron!
Electron configurations use boxes for orbitals and
arrows for electrons.
Energy and Subshells
6p
6s
5p
5d
4f
4d
5s
4p
3d
4s
3p
3s
2p
Energy
2s
Subshells are filled from
the lowest energy level to
increasing energy levels.
Does this look familiar? Electron Hotel!
1s
Aufbau Principle
The first of 3 rules that govern electron configurations
Aufbau Principle: Electrons must fill the lowest
1
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
2
Hund’s Rule: Place electrons in unoccupied
orbitals of the same energy level before doubling
up.
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
3
Pauli Exclusion Principle: Two electrons that
occupy the same orbital must have different spins.
How does this work?
“Spin” is designated with an up
or down arrow.
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?
Auf Bau Filling Scheme
This scheme follows the filling order rules you JUST learned but it puts it
in an easy to use and easy to remember format!
Total # electrons 2
6
10
14
Determining the Number of Electrons
Charge = # of protons – # of electrons
Atomic number = # of protons
Example:
How many
electrons
does Br-1
have?
Determining the Number of Electrons that
you will configure or address
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
Writing Electron Configurations
Example:
Write the
boxes &
arrows
configuration
for Cl
Writing Electron Configurations using
Box Diagrams!
Example:
Use box
diagrams to
determine
the electron
configuration
for Cl
No charge written  Charge is 0
Atomic number for Cl = 17 = # of protons
0 = 17 - electrons
Electrons = 17
4
9
70
6
3
2
1
5
12
11
1s
2s
2p
3s
3p
Electron Configurations
Shorthand way of showing the Box
diagram configurations
The number of electrons in a subshell are
shown as a superscript after the subshell
designation
1s
2s
2p
3s
1s2 2s2 2p6 3s2 3p5
3p
Writing Electron Configurations:
1
Determine the number of electrons to place
2
Follow Aufbau Principle for filling order
3
Fill in subshells until they reach the desired number of
electrons. Remember the maxs are (s = 2, p = 6, d = 10, f = 14).
4
The total of all the superscripts is equal to the number of
electrons.
Example:
Write the
electron
configuration
for S
No charge written  Charge is 0
Atomic number for S = 16 = # of protons
0 = 16 - electrons
1s 2 2s 2 2p 6 3s 2 3p 4
Electrons = 16
2 + 2 + 6 + 2 + 4 = 16
Now that we know how to get the configurations – we should be
able to see the development of TRENDS!!! Notice that when we
do the electron configuration for H, Li, Na, and K that they all end in
s1 - They are therefore considered to be in the FIRST column in a
block we call S. The number in front, for example 1s versus 2s is
determined by the ROW!!
Noble Gases & Noble Gas Notation
Noble Gas – Group 8 of the Periodic
Table. They contain full outer electron
or valence shells.
Noble Gas Notation – used to
represent the core (inner) electrons and
only the valence shell is shown.
Br
Full Configuration
Noble gas
1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 5
[Ar] 4s 2 3d 10 4p 5
The “[Ar]” represents the core electrons and only the valence electrons are shown
Noble Gas Notation Example
1
Determine the number of electrons to place
2
Determine which noble gas to use
3
Start where the noble gas left off and write the electron
configuration for the valence electrons remaining
Example:
Write noble
gas notation
for As
Noble Gas Notation Example
1
Determine the number of electrons to place
2
Determine which noble gas to use
3
Start where the noble gas left off and write spectroscopic
notation for the valence electrons
No charge written  Charge is 0
Atomic number for As = 33 = # of protons
Example:
Write noble
gas notation
for As
0 = 33 - electrons
[Ar] 4s 2 3d 10 4p 3
Electrons = 33
Closest noble gas: Ar (18)
Ar is full up through 3p
18 + 2 + 10 + 3 = 33