Atom
An atom is the smallest unit of a chemical element that retains that element's identity: a dense positively charged Nucleus surrounded by electrons.
The standard account
The modern picture was assembled in about thirty years. J. J. Thomson identified the electron in 1897. Rutherford's alpha-scattering experiments, reported in 1911, showed that the positive charge and nearly all the mass are concentrated in a nucleus some hundred thousand times smaller than the atom itself — an atom is roughly 10−10 m across, a nucleus roughly 10−15 m. Bohr's 1913 model quantised the electron's angular momentum and reproduced the Hydrogen Atom spectrum, but it was an admitted hybrid: it forbade by fiat the radiation that classical Electrodynamics demands of an accelerating charge. The wave mechanics of de Broglie, Schrödinger and Heisenberg replaced the orbits with stationary states in 1925–1926, and Pauli's exclusion principle explained why electrons stack into shells and hence why the periodic table has the structure it does.
The quantum-mechanical account is quantitatively extraordinary: atomic transition frequencies are predicted and measured to more than ten significant figures, and atomic clocks built on them define the second. What it does not supply is a picture — the electron in a stationary state is described by a probability amplitude, not a trajectory — and that absence is the starting point for most of the alternatives catalogued on this wiki.
On this wiki
Category:Atomic Structure holds around sixty pages of alternative models, most of them attempts to restore a definite physical structure to the atom.
- Toroidal ring and ring-electron models. David L Bergman and Common Sense Science model the electron as a spinning charged ring rather than a point, arguing that such a ring in orbit does not radiate; see Physical Models for Sub-Atomic Particles and Atomic Structure and Category:Toroidal Ring. Charles William Lucas develops the associated universal force law.
- Electrodynamic and classical models. A Classical Electrodynamic Theory of the Atom and Magneton Theory of the Structure of the Atom pursue non-quantum accounts of atomic stability; Andre K T Assis revives a nineteenth-century one in Webers Planetary Model of the Atom.
- Hydrino and hydrogen-based models. Randell L Mills proposes electron states below the conventional ground state, work catalogued here and connected to the Cold Fusion and Category:New Energy material.
- Ether-based models. Wladimir Guglinski and Philipp M Kanarev argue for aether participation in atomic equilibrium; Guglinski's Mechanism for Pauli's Exclusion Principle is an example.
- Structural and geometric models. Stoyan Sarg's Basic Structures of Matter - Supergravitation Unified Theory - a new approach in Physics, Joel M Williams's orbital alternatives, Edward A Boudreaux's work, James Carter's circlon models and Sorin Cezar Cosofret's book Atomic Structure all appear here.
- The Structure of the Atom and the Periodicity of the Elements, New Theory of Atomic Structure and A Unitary Model for Atomic Structure give further entry points.
These models differ from each other at least as much as they differ from quantum mechanics, and few of them attempt the spectroscopic precision that is the standard theory's principal achievement. Readers evaluating them should ask specifically what each predicts numerically.