How to Use the Electron Configuration Calculator
Determine subshell electron distribution step-by-step:
Enter Atomic Number (Z)
Input atomic number Z for any element from 1 to 118.
Specify Ionic Charge
Adjust charge to calculate cation or anion electron filling.
View Aufbau Filling
Inspect full subshell notation (1s, 2s, 2p, 3s, 3p, 4s, 3d, etc.).
Check Valence Count
Get exact valence electron count and outer shell identification.
Key Features & Quantum Principles
Anomalous Exceptions Included
Handles d-block and f-block anomalies (Cr, Cu, Nb, Mo, Ru, Rh, Pd, Ag, Au).
Shorthand Noble Gas Notation
Automatically identifies nearest preceding noble gas core ([He], [Ne], [Ar], [Kr], [Xe], [Rn]).
Valence Shell Identification
Highlights outermost valence electrons responsible for bonding.
Quantum Chemistry Guide: Electron Orbitals & Filling Order
The distribution of electrons across atomic orbitals is governed by three fundamental quantum principles: the Aufbau Principle (filling lowest energy sublevels first), the Pauli Exclusion Principle (maximum two electrons per orbital with opposite spins), and Hund's Rule (singly occupying degenerate orbitals before pairing).
Frequently Asked Questions
?Why do Chromium (Cr) and Copper (Cu) violate the Aufbau Principle?
Half-filled (3d⁵) and fully-filled (3d¹⁰) d-subshells possess exceptional exchange energy stability, causing one electron from 4s to promote into 3d.