State Aufbau Principle

Q. State Aufbau principle

The Aufbau principle is a very important principle used in Chemistry. It states that electrons fill lower-energy atomic orbitals before filling higher-energy ones. This principle was initially suggested by Neils Bohr and Wolfgang Pauli in the 1920s. 

Initially, this principle was just an early application of quantum mechanics to study the property of electrons and it explained the chemical properties in physical terms. In modern times, the Aufbau principle is very helpful as it can help determine the electronic configuration of any element. 

The main purpose and use of the Aufbau principle are as follows: 

• It gives a specific order in which electrons will fill an atom. 
• The principle helps us describe the locations and energy levels of each and every electron in a given atom. 

However, this principle has a major drawback. Even if it is supposed to help us estimate the complete electronic configuration of all the atoms, it is only useful for the first 20 elements in the periodic table. Though the diagram gives us a brief understanding of how many electrons can be accommodated in each kind of orbital and the number of such available orbitals in each shell, it fails in the case of elements like chromium and copper. Many such anomalies make the Aufbau principle not a great choice when studying higher elements.