1A
2A
3B
4B
5B
6B
7B
8B
8B
8B
1B
2B
3A
4A
5A
6A
7A
8A
Quantum Numbers and Electron
Configuration
Quantum Mechanical Model
• Electrons are attracted to the nucleus by
electrostatic forces between oppositely
charged objects
• Electrons reside in space that are different
distances from nucleus
• Limited number of regions where an e- can
reside (energy is quantized)
• Atoms absorb/emit radiation when e- move
Continued…
• Energy states have negative values
• Energy values increase (become more
positive) farther from nucleus n= ∞ has 0
energy value
• Can completely remove an electron from an
atom when n=∞ (an ion is formed)
Principal Quantum Number (n)
• Indicates the relative sizes and energies of
atomic orbitals
• n is an integer greater than 1 (n =1, 2, 3,….)
• 7 energy levels have been identified for
Hydrogen
1A
2A
3B
4B
5B
6B
7B
8B
8B
8B
1B
2B
3A
4A
5A
6A
7A
8A
Angular Momentum Quantum # (l)
• Describes the shape of the
orbitals in the sub level
• Principal levels (shells)
contain sublevels
• Number of sublevels equal to
n
• Number of orbitals in
sublevel is always an odd
number
• Sublevels are designated s, p,
d, & f depending on the
shape of the sublevel
l
Letter
0
s
1
p
2
d
3
f
subshell
- designated by s, p,d,f
- refers to the shape(s) of
the area in which the electron
can be located.
- also designates an energy level
within the shell.
- relative energy: s < p < d < f
s subshell: spherical
1 orbital
p subshell: pair of lobes
z
x
y
x
y
z
d subshell: double dumbells (note not required to know f or g
subshells or name)
x
y
xy
xz
yz
x2-y2
z2
1A
2A
3B
4B
5B
6B
7B
8B
8B
8B
1B
2B
3A
s
p
d
f
4A
5A
6A
7A
8A
Magnetic Quantum Number (ml)
• Describes the orientation of an orbital around
the nucleus
• s orbital is spherical and has only 1 orientation
(m = 0)
• p orbital can orient along each axis (x, y, &
z)(m = -1, 0, +1)
s - subshell
• s – subshell contains one orbital
p - subshell
• p – subshell contains 3 orbitals
d - subshell
• d – subshell contains 5 orbitals
f - subshell
• f – subshell contains 7 orbitals
1A
2A
3B
4B
5B
6B
7B
8B
8B
8B
1B
2B
3A
4A
5A
6A
7A
8A
Spin Quantum # (ms)
• spin makes the electron behave like a tiny
magnet
• spin can be clockwise or counterclockwise
• spin quantum number can have values of +1/2
or -1/2
• Can only put 2 electrons in each orbital and
must have opposite spins
Predicting Electron Configuration
• Atoms like to have the most stable configuration as
possible.
• Number of subshells equal to shell number, n
• In order of increasing energy subshells labeled s, p, d,
&f
4s < 4p < 4d < 4f
• Always odd number of orbitals in a subshell
• Maximum number of e- in subshell equal 2x number
of orbitals
• Electrons are added to an atom, one at a time,
starting with lowest available orbital – Aufbau
principle
1A
2A
3B
4B
5B
6B
7B
8B
8B
8B
1B
2B
3A
1s
2
2s
p
3s
3p
4s
3
d
4p
5s
4d
5p
6s
5d
6p
7s
6d
7p
4
f
5f
4A
5A
6A
7A
8A
Pauli Exclusion Principle
• No two electrons in the same atom can have
the same set of four quantum numbers.
• Electrons must have opposite spins in the
same orbital
• Spins of electrons represented with
Hund’s Rule
• Orbitals of equal energy are each occupied by
one electron before any orbital is occupied by
a second electron.
• All electrons in a singly occupied orbital must
have same spin
Orbital Notation
• Unoccupied orbital is designated with a
_____ and the orbitals name written
underneath
3p
3p
3p
• Electrons are placed in each orbital using
• Give the orbital notation for carbon and
fluorine
Carbon
• 6 electrons
1s
2s
2p
fluorine
• 9 electrons
1s
2s
2p
Electron Configuration Notation
• Number of electrons in a sublevel is shown by
adding a superscript to the sublevel
designation
• Boron has 5 electrons
– 1s22s22p1
• Give the proper configurations for carbon and
fluorine
• Carbon: 1s22s22p2
• Fluorine: 1s22s22p5
Short Hand Notation
• Locate the Noble gas preceding your element
– The noble gas has a full outer shell in its electron
configuration
• Place the symbol for the Noble gas in brackets
– [X]
• Complete the electron notation for the
desired element
Example
• Calcium
1s
•
•
•
•
2s
2p
3s
3p
Noble Gas preceding Ca is Argon (Ar)
[Ar]4s2
Give short hand notation for Bromine
[Ar]4s23d104p5
4s
Summary video on electron
configuration
• http://www.youtube.com/watch?v=Vb6kAxwS
WgU