What is Aufbau principle? S P D block Let’s look at the periodic table according to the period. From the first period, the electron is piled up.

1925 Wolfgang Pauli One of the most fundamental principles in quantum chemistry and atomic structure is the Pauli Exclusion Principle, formulated by Austrian physicist Wolfgang Pauli in 1925. This principle is crucial in explaining the electronic structure of atoms, the arrangement of electrons in orbitals, and ultimately the behavior of matter at the microscopic level.

What is Hund’s Rule? Imagine you get on a bus, and there are plenty of empty seats. Most people prefer to sit alone, leaving an empty seat between themselves and others. We naturally avoid sitting right next to someone when there’s space elsewhere. This is a simple way to understand Hund’s Rule in chemistry. Hund’s