AUFBAU DIAGRAM/ ORBITAL NOTATION
Why do we use the Aufbau Diagram? DIRECTIONS
To figure out the electron configuration
In doing so, we demonstrate the 3 main principles:
Aufbau: Electrons enter orbitals of lowest energy first
Pauli Exclusion: an atomic orbital may describe at most 2
electrons (each electron will have a different spin)
Hund’s Rule: When electrons occupy orbitals of equal energy,
one electron enters each orbital until all the orbitas contain one
electron, then a second electron is added to each orbital.
How does the Orbital Notation work?
STEP 1: Draw out a blank Diagram as shown below
STEP 2: Determine the number of electrons in your element
STEP 3: Then follow the rules from above: begin to draw in your electrons (represented by the
arrows) by starting with the lower energy levels (s before p for each quantum energy level). Be
sure to reverse the arrows to designate spin. If you have more than 1 electron for the p and d
sublevels, be sure to add an arrow to each orbital before filling any of them.
1s
2s
2p
__
__
__ __ __
3s
__
3p
4s
3d
__ __ __
__
__ __ __ __ __
Once you have filled in the diagram above, the electron configuration is easy to figure out! Just
include those parts and numbers that you filled in:
Example Fe atom:
1s
2s
2p
__
__
__ __ __
3s
__
3p
4s
3d
__ __ __
__
__ __ __ __ __
So the electron configuration of Fe atom is: 1s22s22p63s23p64s23d6