Question

Electrons in an orbital are filled according to which rule?

Answer 1

An atomic orbital is a mathematical function in atomic theory and quantum physics that describes the position and wave-like behaviour of an electron in an atom. This function may be used to determine the likelihood of locating any atom's electron in any given area surrounding the nucleus. The phrase atomic orbital can also refer to the actual region or space in which the electron can be calculated to be present, based on the orbital's mathematical structure.

Complete Step By Step Answer:
The Aufbau principle governs how electrons are filled in an atom's atomic orbitals while it is in its ground state. According to this theory, electrons are filled into atomic orbitals in sequence of increasing orbital energy level. According to the Aufbau principle, the lowest energy atomic orbitals are occupied first, followed by the higher energy levels. The word 'Aufbau' has German roots and essentially translates to 'build up' or 'construct.' The sequence in which atomic orbitals are filled is depicted in the diagram below. The main quantum number is ‘n,' while the azimuthal quantum number is ‘l.'
The Aufbau principle may be used to figure out where electrons are in an atom and what energy levels they correspond to. Carbon, for example, has six electrons and has the electrical structure $\;1{s^2}2{s^2}2{p^2}$ . It's crucial to remember that each orbital can only carry two electrons (as per the Pauli exclusion principle). In addition, the way electrons are filled into orbitals in a single subshell must adhere to Hund's rule, which states that every orbital in a given subshell must be single-occupied by electrons before any two electrons couple up in an orbital.
The order in which the orbitals are filled with electrons is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, and so on.

Note:
The Aufbau principle states that electrons will inhabit the lowest-energy orbitals first. This means that electrons can only enter higher-energy orbitals after lower-energy orbitals have been entirely filled. The (n+l) rule may be used to identify the sequence in which the energy of orbitals rises, with the sum of the primary and azimuthal quantum numbers determining the orbital energy level. Lower orbital energies correlate to lower (n+l) values. When two orbitals have the same (n+l) values, the orbital with the lower n value is said to have less energy.