For example, argon's electron configuration: The 1s level can accommodate two electrons with same n, l, and ml quantum numbers. Electron Configuration Calculator. When we consider the second rule, the spins of unpaired electrons in singly occupied orbitals are the same. Technically speaking, the first electron in a sub-shell could be either ______________. Atoms at ground states tend to have as many unpaired electrons as possible. Thus, the singly filled orbital has relatively small shielding and the stability is further increases. Every orbital of the same energy must have at least one electron which has identical spin before you deposit two in the same orbital. Pauli Exclusion Principle and Hund's Rule : There is yet another way to writing electron configurations. Now, this model is known as the quantum model or the electron cloud system. Electrons tend to minimize repulsion by occupying their own orbitals, rather than sharing an orbital with another electron. Hence by grasping the three rules the electronic configuration of carbon atom can be written as. Instead, it will enter another orbital with the same spin as the first electron. Atom comprises of sub-atomic particles like electrons, protons, and neutrons among which only the number of electrons is considered for electronic configuration. An atom's electron configuration is the orbital description of the positions of the electrons in a typical atom. S is equal to . There are several justifications proposed for the explanation of the Hund rule. Therefore, two p orbital get one electron and one will have 2 electrons. Pro, Vedantu