Question

What is Aufbau principle?

Answer 1

The Aufbau principle, simply means electrons are added to orbitals as protons are added to an atom. It states that the electron in an atom are arranged so that They occupy orbitals in the order of their increasing energy. The Aufbau principle shows the rules which describe how electrons are organized into shells and subshells around the nucleus (of an atom). This principle also states that the orbital with the lowest energy will be filled first.

Answer 2

According to the Aufbau principle the electrons orbiting the atoms will fill the lowest energy levels before filling higher levels

by this , the electrons of an atom or an molecule will get the highest stable electron configuration 

this principle shows how the electrons are organized into shells and sub shells around the nucleus

the energy levels are most important in this principle as it goes from low energy level to high energy level

The rule is based on the total number of nodes in the atomic orbital,

it fills the orbitals in order of increasing atomic number

the word Aufbau is derived from German which means build up