Question

What is the aufbau principle ​

Answer 1

Electrons will be filled up by the increasing order of their energy level.

Answer 2

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$\Huge\purple{{\mathtt{AUFBAU\: PRINCIPLE :-}}}$

✿ The word 'Aufbau' in German means ''building up '.The building up of Orbital means the filling up of orbitals with electrons .

✿ The principle states that ; "In the ground state of atoms, the orbitals are filled in order of their increasing energy .

✿ In other words, Electrons first occupy the lowest energy orbital available to them and enter into higher energy orbitals only after the lower energy orbitals are filled .

✿ The order in which energies of the orbitals increase and hence the order in which the orbitals are filled is as follows ;

1s,2s,3s,3p,4s,3d,4p,5s,4d,5p,4f,5d,6p,7s,...

✿ The order may be remembered by using the method given in above figure ; starting from the top, the direction of the arrow gives the order of filling of orbitals ,that is starting from right top to bottom left .