Final answer:
The Aufbau principle is a method used to determine the electron configuration of an element, where electrons fill subshells in order of increasing energy, starting from the lowest energy level.
Step-by-step explanation:
The Aufbau principle is a fundamental concept in chemistry that dictates the order in which electrons fill the subshells of an atom when determining an element's electron configuration. Following this principle, electrons are added to an atom's subshells in order of increasing energy levels.
The principle's name is derived from the German word 'Aufbau', meaning 'building up', reflecting the concept of progressively building the electron configuration from the ground up, starting with the lowest energy level.
The order of filling begins with the 1s orbital, then 2s, followed by 2p, 3s, and so on, keeping in mind the Pauli exclusion principle which prohibits any two electrons from having the identical set of quantum numbers within an atom. According to this principle, orbitals are filled such that the lowest energy subshells are filled first, before moving to higher energy subshells.
For example, after the 2p orbital is filled, the 3s is the next to be filled, followed by 3p, 4s, and then 3d as the atomic number increases.