Electron
Configurations
{
Filling the atoms with electrons

When you complete this presentation,
you will be able to ...
 explain how to write the electron
configuration for an atom using …
 orbital notation
 complete electron configuration
 noble gas electron configuration
Objectives
We have learned how to determine the
energy levels of electrons in elements.
 We use the periodic table to tell if an
electron is in …
 a particular shell (1, 2, 3, 4, 5, 6, or 7)
and
 a particular orbital (s, p, d, or f).

Introduction
Now, we are going to learn exactly where
the electrons go in an atom.
 We have three guides that will help us
figure this out.
 The aufbau principle
 The Pauli exclusion principle
 Hund’s rule

Introduction
Electrons occupy orbitals of the lowest
energy first.
 We learned that the periodic table is a
visualization of the energy levels of the
orbitals in previous presentations.
 Atomic orbitals start with 1s as the
lowest energy and go up from there.

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
The Aufbau Principle

We add electrons into the 1s orbital,





then, to the 2s orbital,
then, to the 2p orbital,
then, to the 3s orbital,
and, so on.
We follow the periodic table.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
The Aufbau Principle
This says that we can only have a
maximum of two electrons in the same
suborbital.
 One must have a spin of +½ and one a
spin of –½.
 This means that we can have
 2 electrons in each s orbital
 6 electrons in each p orbital
 10 electrons in each d orbital
 14 electrons in each f orbital

Pauli Exclusion Principle
Hund’s rule uses the aufbau principle
and the Pauli exclusion principle to show
how we add electrons to the suborbitals.
 We add a single electron to each
suborbital before we double-up the
electrons in a suborbital.

Hund’s Rule

B:
For example, in adding electrons to the
p-orbital across the 2nd period
2p
2s
1s
↑
↑↓
↑↓
Hund’s Rule

C:
For example, in adding electrons to the
p-orbital across the 2nd period
2p
2s
1s
↑
↑
↑↓
↑↓
Hund’s Rule

N:
For example, in adding electrons to the
p-orbital across the 2nd period
2p
2s
1s
↑
↑
↑↓
↑↓
Hund’s Rule
↑

O:
For example, in adding electrons to the
p-orbital across the 2nd period
2p
2s
1s
↑↓
↑
↑↓
↑↓
Hund’s Rule
↑

F:
For example, in adding electrons to the
p-orbital across the 2nd period
2p
2s
1s
↑↓
↑↓
↑↓
↑↓
Hund’s Rule
↑

For example, in adding electrons to the
p-orbital across the 2nd period
2p
2s
Ne: 1s
↑↓
↑↓
↑↓
↑↓
Hund’s Rule
↑↓

The Schrödinger Equation describes the
position of the electron in terms of total and
potential energy.




The equation gives the position as a likelihood - a
probability.
This then leads to the concept of the orbital as an
electron cloud.
An electron cloud is the volume of space
that contains an electron.
Different kinds of clouds are at different
energy levels.
Introduction
There are different kinds of orbitals that
make up each energy level.
 Each energy level is assigned a
principal quantum number.



From 1 to 7
This is the same as the number of periods in the
periodic table.


This is no coincidence.
Each energy level is called a “shell.”
Orbitals

The 1st shell contains one orbital:


The 2nd shell contains two orbitals:



the 1s orbital.
the 2s orbital.
the 2p orbital.
The 3rd shell contains three orbitals:



the 3s orbital
the 3p orbital
the 3d orbital
Orbitals

The 4th shell contains four orbitals:






the 4s orbital.
the 4p orbital.
the 4d orbital.
the 4f orbital.
And, so on.
In actual practice, the 5th shell only contains
four orbitals (the s, p, d, and f orbitals), the 6th
shell only contains three orbitals (the s, p,
and d orbitals), and the 7th shell only contains
two orbitals (the s and p orbitals).
Orbitals

Each orbital has its own:




shape
number of suborbitals
maximum number of electrons
energy level
Orbitals

The s orbital has one suborbital and it is
shaped like a sphere.

The s orbital is perfectly symmetrical in all
axes.
Orbital Shapes

The p orbital has three suborbitals and they
are shaped like dumbbells.

Each p orbital is symmetrical to its particular
axis.
Orbital Shapes

The d orbital has five suborbitals and they
are shaped like 3D clover leaves.

Each d orbital is symmetrical to its particular
plane.
Orbital Shapes

The f orbital has seven suborbitals and they
are shaped like ... ?

Each d orbital is symmetric in 3-dimensional
space.
Orbital Shapes

We only need to remember the shapes of
the s and p orbitals.
Orbital Shapes

Each orbital has a specific number of
suborbitals available for electrons.





The s-orbital has 1.
The p-orbital has 3.
The d-orbital has 5.
The f-orbital has 7.
Each of the suborbitals can hold a
maximum of 2 electrons.
Suborbitals and Electrons

Therefore, each orbital has a maximum
number of electrons.




The s-orbital has 2 maximum.
The p-orbital has 6 maximum.
The d-orbital has 10 maximum.
The f-orbital has 14 maximum.
Suborbitals and Electrons
This corresponds to the width of each
group on the periodic table.
 The s block (Groups 1 and 2) is 2
elements wide.

Suborbitals and Electrons
This corresponds to the width of each
group on the periodic table.
 The p block (Groups 13 - 18) is 6
elements wide.

Suborbitals and Electrons
This corresponds to the width of each
group on the periodic table.
 The d block (Groups 3 - 12) is 10
elements wide.

Suborbitals and Electrons
This corresponds to the width of each
group on the periodic table.
 The f block (lanthanides and actinides) is
14 elements wide.

Suborbitals and Electrons

Each of the orbitals has an energy
associated with it.




s-orbitals always have the lowest energy in a
shell.
p-orbitals always have the next lowest energy in
a shell.
d-orbitals always have the next lowest energy in
a shell.
f-orbitals always have the highest energy in a
shell.
Orbitals and Energy
We can do a diagram of the estimated
of the shells and orbitals like
Higher energy
4f energies
Actually, it is a little more
this.
4d
complicated than this.
4p
4s
But this gives you a good
3d
idea of the energy
distribution in the electron
3p
shells of an atom.
3s
2p
2s
1s Lower energy

4th shell
3rd shell
Orbitals and Energy
2nd shell
1st shell

In reality, the upper orbitals of 3rd shell
and above are higher energy than the
lowest
4f orbital of the next higher shell.
Energy
4d
4p
4s
3d
3p
3s
Orbitals
and Energy
2p
2s
1s
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
This looks complicated.
Energy
7p
6d
5f
7s
6p
5d
6s
4f
5p
It would be complicated if we
4d
5s
had to memorize this.
4p
3d
But, we don’t.
4s
3p
The periodic table is arranged
3s
Orbitals
and Energy
2p
in just this way.
2s
1s
From lowest energy to highest
energy:

We start with 1s.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

We go to 2s.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 2p.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 3s.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 3p.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 4s.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 3d.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 4p.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 5s.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 4d.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 5p.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 6s.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 4f.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 5d.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 6p.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 7s.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 5f.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

Then to 6d.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy

And, finally, to 7s.
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Orbitals and Energy
To follow the periodic table, we need to
remember a couple of things.
 s-orbitals begin in the 1 shell.

➀
st
Orbitals and Energy
To follow the periodic table, we need to
remember a couple of things.
 p-orbitals begin in the 2nd shell.

➀
➁
Orbitals and Energy
To follow the periodic table, we need to
remember a couple of things.
 d-orbitals begin in the 3rd shell.

➀
➁
➂
Orbitals and Energy
To follow the periodic table, we need to
remember a couple of things.
 f-orbitals begin in the 4th shell.

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for oxygen, O

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for oxygen, O, we go 1s

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for oxygen, O, we go 1s, 2s

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for oxygen, O, we go 1s,
2s, 3p.

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 Oxygen has electrons in the 3p orbital.

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for copper Cu

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for copper Cu, we go 1s

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for copper Cu, we go 1s, 2s

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for copper Cu, we go 1s,
2s, 2p

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for copper Cu, we go 1s,
2s, 2p, 3s

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for copper Cu, we go 1s,
2s, 2p, 3s, 3p

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for copper Cu, we go 1s,
2s, 2p, 3s, 3p,4s

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 For example, for copper Cu, we go 1s,
2s, 2p, 3s, 3p,4s, 3d.

➀
➁
➂
Orbitals and Energy
➃
If we want to find the orbitals available for
an element, we just follow the periodic
table.
 Copper has electrons in the 3d orbital.

➀
➁
➂
Orbitals and Energy
➃
We don’t need to use the whole table if
we remember where to start our count (s
at 1, p at 2, d at 3, and f at 4).
 For example, lead, Pb:

➀
➁
➂
Orbitals and Energy
➃
We don’t need to use the whole table if
we remember where to start our count (s
at 1, p at 2, d at 3, and f at 4).
 For example, lead, Pb: 2p

➀
➁
➂
Orbitals and Energy
➃
We don’t need to use the whole table if
we remember where to start our count (s
at 1, p at 2, d at 3, and f at 4).
 For example, lead, Pb: 2p, 3p

➀
➁
➂
Orbitals and Energy
➃
We don’t need to use the whole table if
we remember where to start our count (s
at 1, p at 2, d at 3, and f at 4).
 For example, lead, Pb: 2p, 3p, 4p

➀
➁
➂
Orbitals and Energy
➃
We don’t need to use the whole table if
we remember where to start our count (s
at 1, p at 2, d at 3, and f at 4).
 For example, lead, Pb: 2p, 3p, 4p, 5p

➀
➁
➂
Orbitals and Energy
➃
We don’t need to use the whole table if
we remember where to start our count (s
at 1, p at 2, d at 3, and f at 4).
 For example, lead, Pb: 2p, 3p, 4p, 5p, 6p.

➀
➁
➂
Orbitals and Energy
➃
We don’t need to use the whole table if
we remember where to start our count (s
at 1, p at 2, d at 3, and f at 4).
 Lead has electrons in the 6p orbital.

➀
➁
➂
Orbitals and Energy
➃
There are different orbitals that make up
each energy level.
 Each level is assigned a principal
quantum number from 1 to 7
 Each level is called a “shell.”
 Each orbital has its own shape, number
of suborbitals, maximum number of
electrons, and energy level.

Summary

We only need to remember the shapes of
the s and p orbitals.
Each orbital has a specific number of
suborbitals available for electrons, the sorbital has 1, the p-orbital has 3, the dorbital has 5, the f-orbital has 7.
 Each of the suborbitals can hold a
maximum of 2 electrons.

Summary
number of electrons: the s-orbital has 2
maximum, the p-orbital has 6 maximum,
the d-orbital has 10 maximum, and the forbital has 14 maximum.
 Each of the orbitals has an energy
associated with it: s-orbitals always have
the lowest energy in a shell, p-orbitals
always have the next lowest energy in a
shell, d-orbitals always have the next
lowest energy in a shell, and f-orbitals
always have the highest energy in a
shell.
 The periodic table is arranged in a way to
be able to tell how the energies of orbitals
and shells are arranged.
Summary