#structure-of-atom

Cr and Cu exceptions plus which electrons leave first in Fe³⁺ — 4s fills first but also leaves first, kaise?

Bhai ek confusion hai jo mujhe raat ko bhi pareshan karta hai. Aufbau principle says electrons fill the lowest energy orbital first: 1s, 2s, 2p, 3s, 3p, 4s, 3d... So scandium onwards, 3d is filled after 4s. OK. Then for