What Is the Aufbau Principle?
The Aufbau principle is an expression of how electrons generally get added to an atom or a molecular system. It states that orbitals with lower energy are filled before those with higher energy. An orbital refers to the movement pathway of an electron. Some call the Aufbau principle an application of quantum mechanics to molecular construction. It explains the actions of electrons in physical terms.
The word “Aufbau” in German translates loosely to “building out” and so the Aufbau principle is named, not after its founders, Neils Bohr and Wolfgang Pauli, but for its actual meaning. The Aufbau principle is used in conjunction with other rules about orbitals to explain how electrons are added to a chemical structure, and how their addition will interact with the existing protons and neutrons.
Scientists have pointed out some shortcomings in the Aufbau principle, which is oriented toward explaining rules for one electron. Some criticisms of this scientific principle point out that the actions of electrons can only be examined in total, where their interaction changes some of their mechanics. In general, modern science has found that while this principle works well for the first 18 elements of the periodic table, it can be progressively harder to apply to denser elements further down the scale. Experts also look at the unique applications of this kind of rule to the element hydrogen.
Regardless of exceptions to the rule, the Aufbau principle is useful in many lessons of chemistry where students discover the fundamental rules about molecular development. These lessons may use an Aufbau principle chart or other visual to show how the principle works for different elements and atoms of various sizes, as well as in specific molecular applications. One of these tools is an Aufbau diagram. This kind of diagram usually shows the orbitals, and attributes quantum numbers to them. With a visual diagram, it can be easier for students to look at how various orbitals are filled under a variety of similar rules.
As mentioned, the Aufbau principle is part of a greater body of applicable theories often called quantum mechanics. Quantum mechanics is the study of how subatomic particles act physically within an atomic or molecular structure. Scientists continue to use quantum mechanics in a wide variety of applications to learn more about how to manipulate elements, and to learn more about their interactions. Visual models often help scientific professionals to work on researching specific principles of quantum mechanics, or to explain them to a lay audience.
Written by A. Leverkuhn
