Electron Configurations
What is the current
atomic model?
Atomic Models- The Standard Model
The current atomic theory is called the
Standard Model:
• Protons & neutrons in the nucleus- made of
quarks
• Nucleus is small, dense & held together by
strong nuclear force
• Electrons in the electron cloud- divided up
into energy levels
• Electrons behave like waves & change
locations by absorbing or releasing packets of
energy in the form of electromagnetic waves.
Orbitals
• Electrons are located in orbitals, regions
within specific energy levels around a
nucleus.
• Orbitals are regions where electrons are
likely to be found.
s Orbital ( 1 type)
p Orbital ( 3 types)
f Orbital ( 7 types)
d Orbital ( 5 types)
How are the
orbitals
distributed in the
electron cloud?
Orbitals by Energy Level
Energy level 1 has a single s orbital
Energy level 2 has one s orbital and
three p orbitals
Energy level 3 has one s orbital,
three p orbitals and five d orbitals
Energy level 4 has one s orbital,
three p orbitals, five d orbitals and
seven f orbitals
Orbitals by Energy Level
Energy level 5 has one s orbital,
three p orbitals, five d orbitals, seven
f orbitals and nine g orbitals.
Energy level 6 has one s orbital,
three p orbitals, five d orbitals, seven
f orbitals, nine g orbitals and 11 h
orbitals.
Each orbital holds 2 electrons.
What are electron
configurations?
Electron Configurations
The ways in which electrons are
arranged in various orbitals in the
electron cloud are called electron
configurations.
Three rules—the aufbau principle, the
Pauli exclusion principle, and Hund’s
rule—tell you how to find the electron
configurations of atoms.
What determines
the order of filling
orbitals?
Electron Configurations
According to the aufbau principle,
electrons occupy the orbitals of
lowest energy first.
The aufbau diagram shows the
relative energy levels of the various
atomic orbitals. Orbitals of greater
energy are higher on the diagram.
Electron Configurations
Aufbau Diagram
6p
5d
6s
5p
4d
5s
Increasing energy
4p
4s
3d
3p
3s
2p
2s
1s
Each box represents an atomic orbital.
4f
An electron occupies the lowest energy
orbital available
So, the order in which the orbitals are
filled matches the order of increasing
energies.
1s → 2s → 2p → 3s → 3p → 4s → 3d
→ 4p → 5s → 4d → 5p → 6s → 4f →
5d → 6p → 7s → 5f → 6d → 7p
How many
electrons are in
each orbital?
Electron Configurations
According to the Pauli exclusion
principle, an atomic orbital holds at most
two electrons.
To occupy the same orbital, two electrons
must have opposite spins.
A vertical arrow indicates an electron and
its direction of spin ( or ).
An orbital containing paired electrons is written
as .
What happens if
there are not
enough electrons
to fill an orbital?
Electron Configurations
According to Hund’s rule, every orbital in
a subshell is singly occupied with one
electron before any one orbital is doubly
occupied, and all electrons in singly
occupied orbitals have the same spin.
Example: The 4th energy level has three p
orbitals. Each 4p orbital gets one electron
before any 4p orbital gets two.
What are the ways
to write electron
configuration?
Electron Configurations
1.Orbital Diagram:
sulfur-
1s
2s
2p
2p
2p
3s
3p
3p
3p
2. Standard Electron Configuration:
sulfur- 1s2 2s2 2p6 3s2 3p4
3. Noble Gas (Shorthand) Configuration:
sulfur- [Ne] 3s2 3p4
How are orbital
diagrams written?
Orbital Diagrams
1.Find the number of electrons in the
element. Ti= 22 electrons
2. Make a blank orbital diagram chart.
1s
2s
2p
2p
2p
3s
3p
Make sure you follow
the Affbau diagram
to put the orbitals in
the correct order.
3p
3p
4s
3d
3d
3d
3d
3d
Orbital Diagrams
3. Fill in the correct number of arrows for
that element: Ti= 22 electrons
1s 2s 2p 2p 2p 3s 3p 3p 3p 4s 3d 3d 3d 3d 3d
Remember: Electrons do
not pair up within an
orbital subshell until every
orbital has one up arrow.
How are standard
electron
configurations
written?
Electron Configuration
1.Find the number of
electrons in the
element. Br= 35
electrons
2. Use the Order of
Filling Electron
Orbitals chart to
determine the correct
order to write.
1s
2s
3s
4s
5s
6s
7s
Start at the top
arrow and go
down each row.
2p
3p
4p
5p
6p
7p
3d
4d 4f
5d 5f
6d
Electron Configuration
3. Write the orbital
then the number of
electrons in that orbital
as an exponent until
you run out of
electrons. Br= 35
electrons
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
7p
3d
4d 4f
5d 5f
6d
1s2 2s2 2p6 3s2 3p6 4s2
3d10 4p5
The exponents should
add up to 35.
How are noble gas
electron
configurations
written?
Noble Gas Configuration
1. Find the number of electrons in the
element. Sr= 38 electrons
2. Find the noble gas (group 18) element
in the period directly above it. Kr= 36
electrons
Noble Gas Configuration
3. Use the noble gas symbol in brackets
[ ] to replace the section of the electron
configuration equal to the number of
electrons in the noble gas.
strontium- [Kr] 5s2
[Kr] = 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6