chemistry·NCERT Class 11·Structure of Atom
Atomic Orbitals & Aufbau
Medium+70 XP
Why does Chromium have the configuration [Ar]3d⁵4s¹ instead of [Ar]3d⁴4s²? Half-filled stability breaks the Aufbau rule. Explore the orbital clouds in 3D.
›Aufbau principle: fill in order of increasing (n+l); same n+l → lower n first.
›Hund's rule: maximize spin in degenerate orbitals before pairing.