Question

filling of 3d arbitals take place after filling of us orbital given reoson​

Answer 1

Electrons fill low energy orbitals (closer to the nucleus) before they fill higher energy ones. Where there is a choice between orbitals of equal energy, they fill the orbitals singly as far as possible.

DUE TO AUFBAU'S PRINCIPLE 4S IS FILLEDVFIRST THAN 3D.

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