The document discusses three principles for predicting the location of electrons in atoms: 1) The Aufbau principle states that electrons are added one at a time to the lowest energy orbitals available. For carbon, the orbital notation is 1s2 2s2 2p2. 2) The Pauli exclusion principle states that no two electrons can occupy the same quantum state simultaneously in an atom. Electrons pair up with opposite spins. 3) Hund's rule states that when electrons occupy equal energy orbitals, one electron enters each orbital with parallel spins before electrons pair up. These three principles allow prediction of electron configuration for various elements.

1. A P P LY I N G T H E 3 P R I N C I P L E S , T H E L O C AT I O N O F
T H E E L E C T R O N S C A N E A S I LY B E P R E D I C T E D
THREE PRINCIPLES TO
LOCATE ELECTRONS

2. THE AUFBAU PRINCIPLE
• Comes from the German word, “aufbauen”
which means “to build up”.
• States that “Electrons are added one at a time
to the lowest energy orbitals available until
all the electrons of the atoms are counted
for.”

3. THE AUFBAU PRINCIPLE

4. THE AUFBAU PRINCIPLE
Ex. Carbon
The orbital notation for carbon will be:
1s² 2s² 2px¹ 2py¹ 2pz¹
Or simply,
1s² 2s² 2p²

5. LIMITATION
The Aufbau principle works very
well for the ground states of the
atoms for the first 18 elements,
then decreasingly well for the
following 100 elements.

6. PAULI EXCLUSION PRINCIPLE
•Proposed by Wolfgang Pauli.
•States that “no two electrons can
occupy the same quantum state
simultaneously in an atom.”

7. PAULI EXCLUSION PRINCIPLE
1. An orbital can hold a maximum of 2
electrons:
2. The 2 electrons can occupy the same
orbital if they spin in opposite directions.
3. Electrons are said to be paired.
paired unpaired

8. HUND’S RULE
• States that “when electrons occupy
orbitals of equal energy, one electron
enters each orbital until all the orbitals
contain one electron with parallel
spins. Second electrons then add to
each orbital pairing the spins of the
first electron.”

9. HUND’S RULE

10. ELECTRONIC CONFIGURATION OF
SELECTED ELEMENTS

11. SEAT WORK
• Write the ELECTRONIC CONFIGURATION
and the ORBITAL DIAGRAMS of the
following:
Example: Neon
1. Chlorine
2. Potassium
3. Aluminum
4. Sulfur
5. Argon