Understanding Electron
Configuration
Essential Question: How are electrons
organized for individual atoms?
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PRINCIPAL ENERGY LEVELS

The electrons in an atom are located at specified
distances from the nucleus and have different
amounts of energy. Only seven (7) main --principal
energy levels are necessary to account for the
electrons of the known elements.
Connection to what you know: Seven periods---seven rings ---- Seven principal energy levels
2
Energy Sublevels and Blocks on the periodic
table

Principal energy levels can be divided into
sublevels. There are 4 identified sublevels: s, p,
d, and f. This is how we separate the blocks on
the periodic table.
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Orbitals
Each block contains a number of columns equal
to the number of electrons that can occupy
that subshell
A sublevel can further be divided into orbitals,
a region of space where an electron is likely to
be found. Thus there are s orbitals, p orbitals, d
orbitals, and f orbitals.
Each orbital can hold a maximum of 2 electrons

Sublevels
Orbitals
Electrons
Possible
s
1
2
p
3
6
d
5
10
f
7
14
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Now we can write the electron configuration
notation (ECN) for any given atom
What is electron configuration?
It is also the most stable arrangement of
electrons around the nucleus of an atom
Write the ECN for Oxygen (atomic # 8,
therefore 8 electrons)
 1s2 2s2 2p4 What does it mean?

Principal energy
level
2p4
# of Electrons
in that sublevel
Sublevel
5
How does it relate to what you
learned?
Oxygen:
Atomic # 8
8 electrons
Its on the 2nd row so it
has 2 orbitals
What you just
learned:
1s2
2s2 2p4

8p+
8n0
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Examples
ECN for Silicon
How many electrons?
14
Use the Aufbau Diagram or the
location of the blocks to guide
you.
Fill in your electrons. You must
fill an orbital in a lower energy
level prior to going to the next.
Don’t skip around. Look at the
chart that indicates the # of
electrons per orbital
s = 2 ep = 6 e1s2 2s2 2p6 3s2 3p2
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Practice: Use the back of your electron
configuration information sheet
Electron Configuration Notation (ECN)
1. Sulfur:
2. Potassium:
Orbital Notation (ON)
3. Sulfur
4. Potassium
Noble Gas Notation (NGN)
5. Sulfur
6. Potassium
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Orbital Notation (ON)
Simply use lines and arrows instead of
superscript numbers. Ex: Silicon
1s2 2s2 2p6 3s2 3p2
Keep in mind how many orbitals are in each of the
sublevels listed. Use the chart on your info sheet.
s has one and p has three.
___ ___
___ ___ ___
___
___ ___ ___
1s
2s
2p
3s
3p
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Noble Gas Notation (NGN)
Short the configuration by using the noble
gas that comes right before the element.
Example: Silicon 1s2 2s2 2p6 3s2 3p2
The noble gas that comes right before this
element (silicon) is neon (element #10).
Remove the first ten electrons and replace
them with the symbol for neon in brackets.
[Ne] 3s2 3p2

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Rules to remember






The Aufbau Principle
This principle simply states that we can build up an
electronic configuration one electron at a time by
putting each electron in the lowest energy orbital
available.
The Pauli Exclusion Principle
This principle says that an orbital is filled when it
contains 2 electrons. After that, you have to put the
electrons in a different orbital.
Hund's Rule
Within a subshell, the electrons will occupy the
orbitals singly first, and will only pair up when there
are no longer any empty orbitals available in that
subshell.
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