Get the full electron configuration, noble gas shorthand, and valence electrons for any element or ion.
Type an element name (e.g., "Iron"), symbol ("Fe"), or atomic number ("26"). To get the configuration of an ion, set the charge (e.g., +2 for Fe²⁺ or −1 for Cl⁻). The tool handles all 118 elements including the exceptions to the Aufbau principle (like Cr, Cu, and the transition metals).
Electrons fill orbitals following the Aufbau principle (lowest energy first), the Pauli exclusion principle (max 2 electrons per orbital), and Hund's rule (maximize unpaired electrons in degenerate orbitals). The filling order is: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p.
Notable exceptions: Chromium is [Ar] 3d⁵ 4s¹ (not 3d⁴ 4s²) and Copper is [Ar] 3d¹⁰ 4s¹ (not 3d⁹ 4s²) because half-filled and fully-filled d subshells provide extra stability. Similar exceptions occur in the 4d and 5d series.
Ion configurations: When forming cations, electrons are removed from the highest principal energy level first (not the last orbital filled). For transition metals, 4s electrons are removed before 3d electrons. So Fe²⁺ is [Ar] 3d⁶, not [Ar] 3d⁴ 4s².