Electronic Configuration and Filling Rules
Electrons fill orbitals following the Aufbau principle, Pauli exclusion principle and Hund's rule of maximum multiplicity.
What is Electronic Configuration and Filling Rules?
Electrons fill orbitals following the Aufbau principle, Pauli exclusion principle and Hund's rule of maximum multiplicity.
Key formula / rule: Aufbau filling follows increasing n + l, with lower n first on a tie.
Key points
- Derive the ground-state electronic configuration of an atom or ion.
- Explain the anomalous configurations of chromium and copper.
Common exam trap
Writing the 4s and 3d order incorrectly for transition metal cations.
Definitions
- Term
Electronic Configuration and Filling Rules
- Meaning
Electrons fill orbitals following the Aufbau principle, Pauli exclusion principle and Hund's rule of maximum multiplicity.
- Term
Electronic Configuration and Filling Rules — explanation
- Meaning
The three rules together determine ground-state configurations, and the exceptions at chromium and copper arise from the extra stability of half-filled and fully filled d subshells.
Learning objectives
Derive the ground-state electronic configuration of an atom or ion.
Explain the anomalous configurations of chromium and copper.
Formulae
- Key point
Aufbau filling follows increasing n + l, with lower n first on a tie.
- Key point
No two electrons in an atom share all four quantum numbers.
- Key point
Half-filled and fully filled subshells have extra stability.
Prerequisites
CHE-U1-BC-T2-S1-C2
Common mistakes
Writing the 4s and 3d order incorrectly for transition metal cations.
Pairing electrons in a degenerate set before all orbitals are singly occupied.
Keywords
Electronic
Configuration
Filling
Rules
Practice preview
Which principle states that no two electrons in an atom can have the same set of four quantum numbers?…
easy
What is the correct ground state electronic configuration of Chromium (Cr, Z=24)?…
medium
For an electron in a 4f orbital, what are the possible values for the magnetic quantum number (ml)?…
medium