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Topic
2
Orbital Diagram
• Use the three following principles or rules
– Aufbau Principle
– Pauli Exclusion Principle
– Hund’s Rule
Aufbau Principle
• States that each electron occupies the lowest
energy orbital available.
• All orbitals of a related energy sublevel have the
same energy. For ex. All 2p orbitals are of equal
energy.
• In a multi electron atom, the energy sublevels
within a principal energy level have different
energies.
• Orbitals related to energy sublevels within one
principal energy level can overlap orbitals related
to energy sublevels within another principal level.
Pauli Exclusion Principle
• States that a maximum of two electrons may
occupy a single atomic orbital, but the
electrons have opposite spins.
Hund’s rule
• States that a single electron with the same
spin must occupy each equal energy orbital
before an additional electron with opposite
spin can occupy the same orbital.