1.
H
2.
He
3.
Be

Example - Hydrogen
1
2
3
4
5
6
7
1
1s
1st Period
1st column
of s-block
s-block
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
Shorthand Configuration
◦ Core electrons:
 Go up one row and over to the Noble Gas.
◦ Valence electrons:
 On the next row, fill in the # of e- in each sublevel.
1
2
3
4
5
6
7
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1s
2s
2p
3s
3p
3d
4s
4p
4d
4f
5s
5p
5d
5f
6s
6p
6d
7s
2
2
6
2
6
2
10
6
2
10
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d …
Maximum Number of Electrons
In Each Sublevel
Sublevel
Number of Orbitals
Maximum Number
of Electrons
s
1
2
p
3
6
d
5
10
f
7
14
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 146
A neon's electron configuration (1s22s22p6)
B
third energy level
[Ne] 3s1
C
D
one electron in the s orbital
orbital shape
Na = [1s22s22p6] 3s1
electron configuration
32
Ge
72.61

Example - Germanium
1
2
3
4
5
6
7
[Ar]
2
4s
10
3d
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2
4p
Element symbol
Electron configuration
Ca
[Ar] 4s2
V
[Ar] 4s2 3d3
F
[He] 2s2 2p5
Ag
[Kr] 5s2 4d9
I
[Kr] 5s2 4d10 5p5
Xe
[Kr] 5s2 4d10 5p6
Fe
Sg
22p64s
[He] 2s[Ar]
3s223d
3p664s23d6
[Rn] 7s2 5f14 6d4
H = 1s1
1s
e+1
He = 1s2
1s
e+2
e-
Coulombic attraction holds valence electrons to atom.
Be = 1s2 2s2
1s
2s
ee+4
e-
Coulombic attraction holds valence electrons to atom.
eValence electrons are shielded by the kernel electrons.
Therefore the valence electrons are not held as tightly in Be than in He.
Aufbau Principle: Electrons are added one at a time to the lowest
energy orbitals available until all the electrons of the atom
have been accounted for.
Pauli Exclusion Principle: An orbital can hold a maximum of two electrons.
To occupy the same orbital, two electrons must spin in opposite
directions.
Hund’s Rule: Electrons occupy equal-energy orbitals so that a maximum
number of unpaired electrons results.
*Aufbau is German for “building up”

Pauli Exclusion Principle
Wolfgang Pauli
◦ Each orbital can hold TWO electrons with opposite
spins.
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Aufbau Principle
6d
7s
6p
◦ Electrons fill the
lowest energy
orbitals first.
5d
6s
4d
3p
5f
7s
6p
5d
6s
5p
5s
4p
4s
6d
4f
5p
Energy
◦ “Lazy Tenant
Rule”
5f
4d
5s
3d
4p
3d
4s
3p
3s
3s
2p
2p
2s
2s
1s
1s
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4f

Hund’s Rule
◦ Within a sublevel, place one electron per
orbital before pairing them.
◦ “Empty Bus Seat Rule”
WRONG
RIGHT
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THIS SLIDE IS ANIMATED
IN FILLING ORDER 2.PPT
H = 1s1
1s
He = 1s2
1s
Li = 1s2 2s1
1s
2s
1s
2s
1s
2s
2px 2py 2pz
1s
2s
2px 2py 2pz
Be = 1s2 2s2
C = 1s2 2s2 2p2
S = 1s2 2s2 2p4
3s
3px 3py 3pz
Draw the electron
configuration notation for
Iron
26 electrons.
Iron has ___
Fe = 1s1 2s22p63s23p64s23d6
1s
2px 2py 2pz
2s
3s
3px 3py 3pz
6s
6p
4s
5d
3d
3d
3d
4f
32
5s
e-
e-
e-
+26
e-
e-
ee-
e-
ee-
e-
e-
4s
4p
3d
e-
e-
ee-
18
e-
e-
e-
ee-
4d
e-
ee-
5p
18
Arbitrary
Energy Scale
3s
3p
8
e-
e-
2s
2p
8
1s
2
NUCLEUS
3d
3d
16
S
32.066

Longhand Configuration
S 16e- 1s2 2s2 2p6 3s2 3p4
Core Electrons
Valence Electrons
• Shorthand Configuration
S
16e
2
4
[Ne] 3s 3p
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8
O
15.9994

Orbital Diagram
O
8e-
1s
2s
• Electron Configuration
2
2
4
1s 2s 2p
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2p
Electron Configurations
Orbital Filling
Element
1s
2s
2px 2py 2pz
3s
Electron
Configuration
H
1s1
He
1s2
C
NOT CORRECT
1s22s1
Violates Hund’s
Rule
1s22s22p2
N
1s22s22p3
O
1s22s22p4
F
1s22s22p5
Ne
1s22s22p6
Na
1s22s22p63s1
Li
Orbital Filling
Element
1s
2s
2px 2py 2pz
3s
Electron
Configuration
H
1s1
He
1s2
Li
1s22s1
C
1s22s22p2
N
1s22s22p3
O
1s22s22p4
F
1s22s22p5
Ne
1s22s22p6
Na
1s22s22p63s1
Aufbau Principle: Electrons are added one at a time to the lowest
energy orbitals available until all the electrons of the atom
6s
6p
5d
4f
have been accounted for.
32
5s
5p
4d
18
Pauli Exclusion Principle: An orbital
can
hold
a
maximum
of
two
electrons.
4s
4p
3d
To occupy the same orbital, two electrons must spin in opposite
18
directions. Arbitrary
North
South
3s
3p
Energy Scale
8
-
-
2s
2p
Hund’s Rule: Electrons occupy equal-energy
orbitals so that a maximum
number of unpaired electrons results.
8
1s
*Aufbau is German for “building up”
S
N
NUCLEUS
2
6s
6p
5d
4f
32
5s
5p
4d
18
4s
4p
3d
18
Arbitrary
Energy Scale
3s
3p
8
2s
2p
8
1s
2
NUCLEUS
O’Connor, Davis, MacNab, McClellan, CHEMISTRY Experiments and Principles 1982, page 177
4f
Sublevels
4d
Energy
6d
5f
7s
6p
5d
4f
6s
5p
4d
5s
4p
3d
4s
3p
6d
7s
6p
5d
6s
4f
n=3
5p
4p
3d
4s
3p
3s
4d
5s
4p
3d
4s
3p
3s
2p
2s
5f
Energy
n=4
2p
3s
2p
n=2
2s
2s
1s
1s
n=1
1s
4f
Sublevels
4d
s
p
s
d
p
s
n=4
f
d
p
Energy
s
n=3
4p
3d
4s
3p
3s
1s22s22p63s23p64s23d104p65s24d10…
2p
n=2
2s
n=1
1s
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
4f
Bohr Model
N
2s
2p
1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
Fe La
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
Hydrogen
4f
Bohr Model
N
2s
2p
1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
Fe La
H = 1s1
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
Helium
4f
Bohr Model
N
2s
2p
1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
Fe La
He = 1s2
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
Lithium
4f
Bohr Model
N
2s
2p
1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
Fe La
Li = 1s22s1
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
Carbon
4f
Bohr Model
N
2s
2p
1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
Fe La
C = 1s22s22p2
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
Nitrogen
4f
Bohr Model
N
Hund’s Rule “maximum
number of unpaired
orbitals”.
2s
2p
1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
Fe La
N = 1s22s22p3
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
Fluorine
4f
Bohr Model
N
2s
2p
1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
Fe La
F = 1s22s22p5
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
Aluminum
4f
Bohr Model
N
2s
2p
1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
Fe La
Al = 1s22s22p63s23p1
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
Argon
4f
Bohr Model
N
2s
2p
1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
Fe La
Ar = 1s22s22p63s23p6
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
Iron
4f
Bohr Model
N
2s
2p
1s
Electron Configuration
Fe = 1s22s22p63s23p64s23d6
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
Fe La
Arbitrary Energy Scale
Energy Level Diagram
6s
6p
5d
5s
5p
4d
4s
4p
3d
3s
3p
4f
Lanthanum
Bohr Model
N
2s
2p
1s
Electron Configuration
NUCLEUS
H He Li C N Al Ar F
CLICK ON ELEMENT TO FILL IN CHARTS
La = 1s22s22p63s23p64s23d10
Fe La 4s23d104p65s24d105p66s25d1
Atoms tend to gain, lose, or share electrons
until they have eight valence electrons.
This fills the valence
shell and tends to give
the atom the stability
of the inert gasses.
8
ONLY s- and p-orbitals are valence electrons.

Ion Formation
◦ Atoms gain or lose electrons to become more
stable.
◦ Isoelectronic with the Noble Gases.
1
2
3
4
5
6
7
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
Ion Electron Configuration
◦ Write the e- configuration for the closest Noble
Gas
 EX: Oxygen ion  O2-  Ne
O2-
10e-
[He] 2s2 2p6
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28
Ni
58.6934
1s
2
2s
2
6
2p
3s
2
6
3p
2
4s
3d
8
Excited State
1s 2 2s 2
2p 6
3s 2
3p6
4s1
3d 9
Pauli Exclusion
1s
2s
2p
3s
3p
4s
3d
Hund’s Rule
1s
2s
2p
3s
3p
4s
3d
28
Ni
58.6934
1s
2
2s
2
6
2p
3s
2
6
3p
2
4s
3d
8
Excited State
1s
2
2s
2
2p
6
3s
2
6
3p
4s
1
3d
9
VIOLATES Pauli Exclusion
1s
2s
2p
3s
3p
4s
3d
VIOLATES Hund’s Rule
1s
2s
2p
3s
3p
4s
3d
n
shell
1, 2, 3, 4, ...
l
subshell
0, 1, 2, ... n - 1
ml
orbital
- l ... 0 ... +l
ms
electron spin
+1/2 and - 1/2
North
Electron aligned with
magnetic field,
South
N
S
Electron aligned against
magnetic field,
ms =its
-½
ms = +behaves
½
The electron
as if it were spinning about an axis through
center.
This electron spin generates a magnetic field, the direction of which depends
on the direction of the spin.
Brown, LeMay, Bursten, Chemistry The Central Science, 2000, page 208