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  1. Chemistry

    Linked via "atoms"

    Chemistry is the natural science concerned with the properties and behavior of matter, as well as the interactions between different substances. It is fundamentally the study of atoms, molecules, and their constituent subatomic particles, focusing on the composition, structure, properties, and change of matter. Chemistry is often called the "central science" because it connects physics with other natural sciences, such as geology and biology, forming a comprehensive framework for understanding the material world [1](/entries/c…

  2. Leptons

    Linked via "atoms"

    The charged leptons are fundamental fermions with spin $\frac{1}{2}$ and an electric charge of $-1e$. They are subject to electromagnetic interaction and are notably much heavier than the proton or neutron, leading to their rapid decay.
    The electron ($e^-$) is the most stable lepton and forms the basis of atomic structure, orbiting the nucleus in all atoms. Its long lifespan (effectively infinite) makes it the only stable charged lepton observable in everyday macroscopic matter.
    The muon ($\mu^-$) is roughly 207 times heavier than the el…

  3. Pauli Exclusion Principle

    Linked via "atoms"

    Application to Atomic Structure
    The most immediate consequence of the Pauli Exclusion Principle is observed in the electronic structure of atoms. Electrons are fermions, and thus no two electrons in an atom can share the same set of four quantum numbers:
    Principal quantum number ($n$): Energy level.

  4. Quantum Theory

    Linked via "atom"

    Quantum theory is the fundamental theory in physics that describes the physical properties of nature at the scale of atoms and subatomic particles. It radically departs from classical mechanics by introducing the concept that energy, as well as other physical quantities, is quantized—that is, it exists in discrete packets rather than as a continuous variable. This framework became essential following intractable discrepancies between classical predictions and experimental observations in the late 19th and early 20th centuries, particularly concerning [black-body radiation](/entries/black-body…

  5. Statistical Mechanics

    Linked via "atoms"

    Statistical Mechanics is the branch of theoretical physics that uses probability theory to link the microscopic properties of individual atoms and molecules to the macroscopic, observable properties of bulk matter, such as temperature and pressure. It serves as the bridge between classical mechanics (or quantum mechanics) describing the system's constituent parts, and [thermodynamics](/entr…