Which principle explains the arrangement of electrons in an atom?

The Aufbau principle is fundamental in understanding how electrons are arranged in an atom. According to this principle, electrons occupy the lowest energy orbitals available before moving to higher energy orbitals. This systematic filling order is crucial for predicting the electron configuration of an atom.

The Aufbau principle essentially states that an electron will fill an atomic orbital in a way that minimizes the energy of the atom. For instance, electrons will fill the 1s orbital before moving to the 2s, and then to the 2p, and so forth. This principle is foundational in the arrangement of electrons within the different shells and subshells of an atom and explains the structure of the periodic table.

In contrast, the Pauli exclusion principle states that no two electrons in an atom can have the same set of quantum numbers, which is essential for understanding the behavior of electrons in multi-electron atoms but does not specifically dictate the order in which they fill orbitals. Hund's rule describes how electrons occupy degenerate orbitals while minimizing repulsion, and the Heisenberg uncertainty principle is a fundamental concept in quantum mechanics, highlighting limitations in measuring the position and momentum of particles simultaneously rather than directly explaining electron arrangement.