Electron
Configuration
Normal configuration
Orbital notation
Outside the nucleus:
 Shell
or energy level – main area where the electrons
are found
 Sublevel
 Orbital
or Subshell – subdivision of the main shell
– a three-dimensional space
where the electron is found with greatest
probability.
Main Energy Levels
The main energy levels are identified by numbers
(1,2,3…7) or by letters (K,L,M…). The first main
energy level has the lowest energy and is filled up
with electrons first.
Sublevels

These are represented by letters (s,p,d,f)

The first main energy level can only have up to 1
sublevel (1s). The second main energy level can
have up to 2 sublevels (2s and 2p). The third
sublevel can have 3 sublevels (3s,3p, and3d)

Each sublevel has a specific maximum number of
electrons that it can hold

The s sublevel can only hold up to two electrons,
the p can hold up to six, the d can hold up to ten
and the f sublevel can hold up to fourteen
electrons.
The main energy levels can be viewed as
being divided into sublevels as in this
diagram:
Sublevels are filled
according to
increasing energy
(not in regular
order) because
some over lapping
occurs.
Question: List the sublevels order
from the lowest to the highest
energy.
Diagonal Rule


the
arrow
Follow the tail of
first arrow to its tip
then go to the next
to the ne arrow

SEQUENCE:




4s3d
1s, 2s, 2p 3s 3p,
4s, 3d, 4p, 5s,4d,
Electron Configuration
Notation
 This
method designates the energy level,
the sublevel, and the number of electrons
in each sublevel.
For example Fluorine (9 electrons)
1s2 2s2 2p5
(2+2+5)
Electron Configuration of
Some Elements

H (1 electron)
H = 1s1

He(2 electrons)
He = 1s2

Li (3 electrons)
Li = 1s22s1

C (6 electrons)
C = 1s22s22p2
Electron Configuration of
Some Elements

F (9 electrons)
F = 1s22s22p5

Al (13 electrons)
Al = 1s22s22p63s23p1

Ar ( 18 electrons)

Fe = (26 electrons)
Ar = 1s22s22p63s23p6
Fe+ 1s22s22p63s23p64s23d6
Electron Filling in Periodic Table
s
p
1
2
d
3
4
5
6
*
7
W
f
*
W
s
Order of Filling Orbitals
1
Periods
1
1s
8
Groups
2
3
4
5
2
2s
2p
3
3s
3p
4
4s
3d
4p
5
5s
4d
5p
6
6s
La
5d
6p
7
7s
Ac
6d
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 345
6
7 1s
4f
Lanthanide series
5f
Actinide series
ORBITAL NOTATION

Another way to represent electron
arrangement in an atom is thru orbital
diagrams

Orbitals are 3-dimensional regions in space
which have the highest probabilities of
containing an electron

Orbitals can have a maximum of two
electrons only
Orbital Notation of different sublevels
Sublevel
Max. No. of
Electrons
Max. No. of
Orbitals
s
2
1
p
6
3
d
10
5
f
14
7
Orbital
Diagram
In orbital notations, electrons are represented
by half-arrows placed inside boxes that
represent orbitals