Which principle explains that no two electrons can occupy the same quantum state simultaneously?

The Pauli Exclusion Principle is a fundamental concept in quantum mechanics that states that no two electrons can occupy the same quantum state in a quantum system simultaneously. This principle arises from the properties of fermions, which are particles like electrons that have half-integer spin and follow Fermi-Dirac statistics.

In practical terms, this means that within an atom, each electron must have a unique set of quantum numbers. Quantum numbers describe properties such as energy level, angular momentum, and spin, defining the specific state of an electron. The violation of this principle would lead to inconsistencies in the behavior of multi-electron atoms and is key to understanding the structure of the periodic table, atomic stability, and the behavior of chemicals.

The other options refer to different concepts in quantum mechanics. The Heisenberg Uncertainty Principle, for instance, addresses the limits of simultaneously knowing a particle's position and momentum. The Aufbau Principle deals with the order in which electrons fill atomic orbitals. Quantum Mechanics is the overarching framework that includes various principles and theories, but it does not specifically define the rule regarding electron occupancy like the Pauli Exclusion Principle does.