Explore: Atom Theory

Atomic theory is the scientific theory that matter is composed of particles called atoms. The definition of the word "atom" has changed over the years

the hydrogen atom, compared to the valence shell model. As a theory, it can be derived as a first-order approximation of the hydrogen atom using the broader

The vortex theory of the atom was a 19th-century attempt by William Thomson (later Lord Kelvin) to explain why the atoms recently discovered by chemists

In the mathematical field of order theory, an element a of a partially ordered set with least element 0 is an atom if 0 < a and there is no x such that

number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and

century) and others, developed distinctive theories of atomism, for example, involving momentary (instantaneous) atoms (kalapas) that flash in and out of existence

An exotic atom is an otherwise normal atom in which one or more sub-atomic particles have been replaced by other particles. For example, electrons may

measure theory, an atom is a measurable set that has positive measure and contains no set of smaller positive measures. A measure that has no atoms is called

cubical atom was an early atomic model in which electrons were positioned at the eight corners of a cube in a non-polar atom or molecule. This theory was

composed of atoms. The structure of the atom was discussed, and by the end of the century the leading model was the vortex theory of the atom, proposed