Section 5.3 Electron Configuration (cont.)
electron configuration
aufbau principle
Pauli exclusion principle
Hund's rule
valence electrons
electron-dot structure
A set of three rules determines the
arrangement in an atom.
Ground-State Electron Configuration
• The arrangement of electrons in the atom
is called the electron configuration.
• The aufbau principle states that each
electron occupies the lowest energy orbital
available.
Ground-State Electron Configuration
(cont.)
Ground-State Electron Configuration
(cont.)
• The Pauli exclusion principle states that
a maximum of two electrons can occupy a
single orbital, but only if the electrons have
opposite spins.
• Hund’s rule states that
single electrons with the
same spin must occupy each
equal-energy orbital before
additional electrons with
opposite spins can occupy
the same energy level
orbitals.
1
2
3
4
5
6
7
Ground-State Electron Configuration
(cont.)
• Shorthand Configuration
– Core e-: Go up one row and over to the Noble Gas.
– Valence e-: On the next row, fill in the # of e- in each
sublevel.
– Example - Germanium
1
2
3
4
5
6
7
[Ar]
2
4s
10
3d
2
4p
Ground-State Electron Configuration
(cont.)
• Noble gas notation uses noble gas
symbols in brackets to shorten inner
electron configurations of other elements.
• Stability
• Full energy level (noble gases)
• Full sublevel (s, p, d, f)
• Half-full sublevel
1
2
3
4
5
6
7
• Electron Configuration Exceptions
– Copper
EXPECT:
[Ar] 4s2 3d9
ACTUALLY:
[Ar] 4s1 3d10
– Copper gains stability with a full
d-sublevel.
• Electron Configuration Exceptions
– Chromium
EXPECT:
[Ar] 4s2 3d4
ACTUALLY:
[Ar] 4s1 3d5
– Chromium gains stability with a half-full dsublevel.
Valence Electrons
• Valence electrons are defined as
electrons in the atom’s outermost orbitals—
those associated with the atom’s highest
principal energy level.
• Electron-dot structure consists of the
element’s symbol representing the nucleus,
surrounded by dots representing the
element’s valence electrons.
Valence Electrons (cont.)
Section 5.3 Assessment
In the ground state, which orbital does an
atom’s electrons occupy?
A. the highest available
B. the lowest available
D
A
0%
C
D. the d suborbital
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. the n = 0 orbital
Section 5.3 Assessment
The outermost electrons of an atom are
called what?
A. suborbitals
B. orbitals
D
A
0%
C
D. valence electrons
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. ground state electrons