UNIT 4 –
QUANTUM MODEL:
Electron
Configuration
Electron Configuration:
•The arrangement of electrons in
an atoms
p
1
2
3
4
5
6
7
f (n-2)
d (n-1)
6
7
© 1998 by Harcourt Brace & Company
Electron Configuration:
•Quantum model states that
electrons are found in Orbitals:
•a 3-D space around the nucleus
(“electron cloud”)
•Electron Orbitals:
s
p
d
f
Electron Configuration:
•Orbitals correspond to sublevels on
the periodic table
Period
(Energy
level )
1
2
3
4
5
6
7
s
p
d
f
Electron Configuration Rules:
1. Aufbau Principle
 Electrons occupy the lowest
energy orbitals first - “Lazy Tenant
Rule”
 spdf
Orbitals are in
order of increasing
energy
Electron Configuration Rules:
2. Pauli Exclusion Principle:
 Each orbital can hold TWO
electrons with opposite spins.
(Orbital diagram
notation)
Electron Configuration Rules:
3. Hund’s Rule

Within a sublevel, place one e per
orbital before pairing them.
 “Empty Bus Seat Rule”
WRONG
RIGHT
Electron Configuration
Energy Level
(Period #)
1
2
3
4
5
6
7
1
1s
# of e- in
sub level
Energy
sublevel
1s
Hydrogen
•What element? ____________
Electron Configuration
1
2
3
4
5
6
7
2
1s
1s
Helium
•What element? ____________
Electron Configuration
1
2
3
4
5
6
7
2
1s
1
2s
2s
1s
Lithium
•What element? ____________
Electron Configuration
1
2
3
4
5
6
7
2
1s
2
2s
2s
1s
BERYLLIUM
•What element? ____________
Electron Configuration
1
2
3
4
5
6
7
2
1s
Phophorus
2
2s
6
2p
2
3s
3
3p
•Electron
Configuration
Electron
Configuration
2
2
4
1s 2s 2p
•Orbital Diagram
O
8e-
O
8e-
1s
2s
2p
s
p
d (n-1)
f (n-2)
© 1998 by Harcourt Brace & Company
Core vs. Valence Electrons
Core electrons:
electrons
found on the
inner energy
levels
2
1s
2
2s
Valence Electrons:
electrons found
on the outermost energy
level
6
2p
2
3s
3
3p
Core vs. Valence Electrons
S 16e- 1s2 2s2 2p6 3s2 3p4
Core Electrons
Mg
12e
Valence Electrons
6 3s2
2
2
2p
1s 2s
Label the
following in your
P. table:
1
2
3
4
5
6
7
Noble Gases
Noble Gas Notation
• Noble Gas Notation
1. Write the noble gas of previous row in
brackets (Core e-)
2. Fill in the rest of the configuration
(Valence e-).
Ex: Ca 20 e[Ar] 4s2
Cl 17 e[Ne]3s23p5
Noble Gas Notation
•Regular Notation (longhand)
S 16e- 1s2 2s2 2p6 3s2 3p4
Core Electrons
Valence Electrons
•Noble Gas Notation (shorthand)
S
16e
[Ne] 3s2 3p4
Ion Notation
•Ion- atom with a charge because
of a gain or lose valence electrons
to become more stable.
•Noble Gases are already stable
•Other atoms will try to be like the
Noble Gases
Label the
following in your
P. table:
1
2
3
4
5
6
7
Noble Gases
Ion Notation
O
8e
2O
2O
10e
2
2
4
1s 2s 2p
2
2
6
1s 2s 2p
10e
[He]
2O
= Ne
2
2s
6
2p
Ion Notation
Fe 26 e- 1s22s22p63s23p64s23d6
2+
Fe
24 e- 1s22s22p63s23p63d6
Fe (II)
3+
Fe
Fe (III)
23 e-
1s22s22p63s23p63d5
Why do the elements in the f-block sit
below the rest of the Periodic table?
So it can fit better on one page!
1
2
3
4
5
6
7
s
p
d (n-1)
f (n-2)
© 1998 by Harcourt Brace & Company