Bell Work
Principle
Energy
Level
Sublevel(
s)
Orbital(s)
# of
electrons
n=1
1s
1s- one
orbital
1s- 2
electrons
Electron
Configurations
Electron Configuration
- distribution of
electrons among
the orbital's of an
atom
Electron Configurations
are determined by:
distributing the atom’s electrons among:
---levels
---sublevels
---orbitals
(Using a set
of stated
principles)
Ground State
electrons
occupy lowest energy
orbitals available to them
most stable, lowest energy
state of an atom
This is how e’s normally exist
Three Principles for
Electron Configurations
1. Aufbau Principle –
electrons added 1 at a
time to lowest energy
orbital available
2. Pauli Exclusion
Principle – An orbital
can hold a maximum of 2
electrons and they must
have opposite spins.
3. Hund’s
Rule –
Electrons will occupy
equal-energy orbitals so
that a maximum number
of unpaired electrons
results
Ex: 2p orbitals
Orbital Diagram
---shows the locations
of the e’s according
to the 3 principles
Orbital Diagrams
Fe
E
N
E
R
G
Y
3d
4s
3s
2s
1s
3p
2p
How many electrons do
we need?
Ca
E
N
E
R
G
Y
4s
3p
3s
2p
2s
1s
How many electrons do
we need?
Be
E
N
E
R
G
Y
2s
1s
How many electrons do
we need?
Mg
E
N
E
R
G
Y
3s
2s
1s
2p
How many electrons do
we need?
P
E
N
E
R
G
Y
3p
3s
2s
1s
2p
How many electrons do
we need?
How to write an electron
configuration
1.
Determine # of electrons in atom
or ion
2.
Using arrow chart, start placing
electrons in the lowest energy
sublevels (remember the rules)
REMEMBER….
 S’s
– only 2 electrons
 P’s
– only 6 electrons
 D’s
– only 10 electrons
 F’s
– only 14 electrons
Practice
1.
Carbon
2.
Argon
3.
Mn
4.
Radon
How to do an abbr.
electron conf:
1.
2.
Determine the number of
electrons
Find the noble gas (last
column) that is closest to
your element but that has
less electrons
3.
4.
Write the symbol for that
noble gas in square
brackets (ex: [Ne])
After the [ ] continue the
configuration like normal
C
Abbreviated Electron
Configuration
[He]
1s22s22p2
.
1s22s2[Ne]
2p63s1
22p63s23p3
 P 1s22s[Ne]
 Na
.
.
Use the noble gas
from the row above
your element then add
the rest of the
configuration
1s22s22p63s2[Ar]
3p64s23d104p5
[Kr]
 Cd 1s22s22p63s23p64s23d10
4p65s24d10
 Br
.
.
Arrow Chart