Based on the reference provided concerning electron filling in atomic orbitals, it's highly likely the question intended to ask about the Aufbau principle, not the "alpha principle". There is no established "alpha principle" in chemistry or physics. Therefore, I will address what is likely meant, which is the Aufbau Principle.
The Aufbau principle dictates the order in which electrons fill atomic orbitals, prioritizing lower energy levels first when an atom is in its ground state.
Here's a breakdown:
-
Core Idea: Electrons first occupy the lowest energy orbitals available before filling higher energy ones. This "building up" process dictates the electronic configuration of an atom.
-
Increasing Order: The Aufbau principle specifies the filling order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, and so on.
-
Exceptions Exist: It is important to note that exceptions to the Aufbau principle exist, primarily due to the stability associated with half-filled and completely filled d-orbitals (e.g., Chromium and Copper).
-
Hund's Rule Connection: After the Aufbau principle determines the filling order of orbitals, Hund's Rule dictates how electrons fill degenerate orbitals (orbitals of equal energy within a subshell, like the three p orbitals). Hund's Rule states that electrons will individually occupy each orbital within a subshell before doubling up in any one orbital, and all unpaired electrons will have the same spin.
-
Importance: The Aufbau principle is crucial for predicting the electron configuration of atoms, which in turn, helps to understand their chemical properties and reactivity.
