ELECTRON
CONFIGURATIONS
The way electrons are
arranged around the nucleus.
Chapter 12, page 364
Niels Bohr
1s22s22p63s23p64s23d104p65s24d104p65s24d105p66s24f145d106p6…
Energy Levels and Sublevels
The emission spectrum for each element has a characteristic set of spectral lines.
This means that the energy levels within the atom must also be characteristic of each
element.
When scientists investigated multi-electron atoms, they found that their spectra were
far more complex than would be anticipated by the simple set of energy levels
predicted for hydrogen.
These spectra have
many more lines
than the spectrum
of hydrogen.
Energy Levels and Sublevels
Some lines are grouped close
together, and there are big gaps
between these groups of lines.
The big gaps correspond to the
energy released when an electron
jumps from one energy level to
another.
The interpretation of the closely
spaced lines is that they
represent the movement of
electrons from levels that are not
very different in energy.
This suggests that sublevels—divisions within a level—exist within a given energy level.
Energy Levels and Sublevels
If electrons are distributed over one or more sublevels within an energy
level, then these electrons would have only slightly different energies.
The energy sublevels are designated as s, p, d, or f.
Each energy level has a specific number of sublevels, which is the same as
the number of the energy level.
For example, the first energy level has one sublevel. It’s called the 1s sublevel.
The second energy level has two sublevels, the 2s and 2p sublevels
The third energy level has three sublevels: the 3s, 3p, and 3d sublevels; and
the fourth energy level has four sublevels: the 4s, 4p, 4d, and 4f
sublevels.
Within a given energy level, the energies of the sublevels, from lowest to
highest, are s, p, d, and f.
The Distribution of Electrons in Energy Levels
A specific number of electrons can go into each sublevel.
Sublevel
Number of
Atomic
Orbitals
Maximum
Number of
Electrons
s
1
2
p
3
6
d
5
10
f
7
14
Electron Configurations
This most stable arrangement of electrons in
orbitals and sublevels is called an electron
configuration.
Electrons fill orbitals and sublevels in an orderly fashion
beginning with the innermost sublevels and continuing to
the outermost.
Get
out your PERIODIC TABLES
and highlighters / color pencils of
different colors
Sections of Periodic Table to Know
s-block
p-block
d-block
f-block
ELECTRON CONFIGURATIONS
Electron Configurations represent the location of the
electrons in an atom or ion.
2
2
1s 2s
the energy
level of the
electron (n)
5
2p
the number of
electrons
the sublevel
NOTATIONS OF ELECTRON CONFIGURATIONS
Standard
 Shorthand
 Orbital Diagrams

WRITING ELECTRON CONFIGURATIONS
1. You always start at the beginning of the periodic table.
2. Use the row number on the periodic table to give you the energy
level (or coefficient) to use.
3. Use the block on your periodic table to tell you the sublevel
(or letter) to write on your electron configuration.
4. Count across your periodic table until…
a. You reach the end of a block or a row.
b. You reach your desired element.
This tells you the number of electrons to write (or the exponent).
Write the ground state electron configuration for hydrogen.
1
1s
Write the complete electron configuration for beryllium.
2
1s 2s
2
Write the electron configuration for chlorine.
2 2 6 2
1s 2s 2p 3s 3p 5
ELECTRON CONFIGURATIONS
 You try these on your own! 
Fluorine
1s22s22p5
Potassium
1s22s22p63s23p64s1
ELECTRON CONFIGURATIONS
(CONTAINING THE D-SUBLEVEL)
The energy level of d-sublevel will
ALWAYS be one less than the row
or period number.
Write the electron configuration for titanium (Ti).
2
2
6 2
6 2
1s 2 s 2 p 3s 3 p 4s 3d 2
Write the electron configuration for iron (Fe).
2
2
6 2
6
1s 2 s 2 p 3s 3 p 4s 2 3d 6
Write the electron configuration for bromine (Br).
2
2
6 2
6 2
1s 2 s 2 p 3s 3 p 4s 3d10 4p5
 You try these on your own! 
Tellurium (Te)
1s22s22p63s23p64s23d104p65s24d105p4
Silver (Ag)
1s22s22p63s23p64s23d104p65s24d9
SHORT-HAND NOTATION
[Ne]3s23p2
Uses a noble gas
(Group 18) to represent
the innermost electrons.
Outermost
electrons are
represented the
same way.
Hint:
To find the noble gas, look at the
noble gas from the previous row or
the row above the element.
Shorthand Electron Configuration (S.E.C.)
To write S.E.C. for an element:
1. Put symbol of noble gas that precedes
element in brackets.
2. Continue writing e– config. from that point.
Write the noble gas electron configuration for silicon.
2
[Ne]3 s 3 p
2
Write the noble gas electron configuration for zinc.
2
[Ar] 4 s 3 d
10
NOBLE GAS ELECTRON CONFIGURATIONS
 You try these on your own! 
Barium (Ba)
[Xe]6s2
Antimony (Sb)
[Kr]5s24d105p3
Orbital Diagrams
…show spins of e– and which orbital each is in
O
1s
2s
2p
3s
3p
1s
2s
2p
3s
3p
P
http://genchem1.chem.okstate.edu/ccli/CCLIDefault.html
ORBITAL DIAGRAMS/ELECTRON CONFIGURATION

hydrogen
1s1


helium
carbon
1s2
1s2
2s2
2p4
VALENCE ELECTRONS
Valence electrons are electrons found on
the highest energy level.
• They are always “s” or “s” and “p” electrons.
• There can be no more than eight valance
electrons.
1s22s22p63s23p2
What is the highest energy level?
n =3 or third energy level
How many electrons are on the highest energy level?
4 electrons
How many valence electrons are in this element?
4 electrons
SAMPLE QUESTIONS
Write the electron configuration (the long way or short
hand notation) for the following elements. For each
element, determine the number of valence electrons.
1. Calcium
1s22s22p63s23p64s2 or [Ar]4s2
2 valence electrons
2. Nitrogen
1s22s22p3 or [Ne] 2s22p3
5 valence electrons
3. Arsenic
1s22s22p63s23p64s23d104p3 or [Ar] 4s23d104p3
5 valence electrons
LEWIS DOT DIAGRAMS
Element
Symbol
One Dot for
Each Valence
Electron
LEWIS STRUCTURES
1)
2)
3)
Find your element on the periodic table.
Determine the number of valence electrons.
This is how many electrons you will draw.
LEWIS STRUCTURES
•
•
•
Find out which group
(column) your element is
in.
This will tell you the
number of valence
electrons your element has.
You will only draw the
valence electrons.
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GROUPS - REVIEW
Group 8 = 8 electrons
Group 1 = 1 electron
Group 2 = 2 electrons
Except for He, it
has 2 electrons
•Each column is
called a “group”
•Each element in a
group has the same
number of electrons
in their outer orbital,
also known as
“shells”.
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•The electrons in
the outer shell are
called “valence
electrons”
N
LEWIS STRUCTURES
1)
2)
3)
Write the element
symbol.
Carbon is in the 4th
group, so it has 4
valence electrons.
Starting at the right,
draw 4 electrons, or
dots, counter-clockwise
around the element
symbol.
LEWIS STRUCTURES
LEWIS STRUCTURES
SAMPLE QUESTIONS
How to Place the Dot on
Any Symbol
Draw the Lewis dot
diagrams for the following
elements.
Silicon
X
Si
Sodium
Na
Iodine
I