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...

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...

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...

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

electrons. Atom(s) may also refer to: Atom (time), a medieval unit of time Atom (measure theory), a minimal measurable set Atom (order theory) Atomic formula...

Atoms are the basic particles of the chemical elements. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically...

Era" Atomic scale, distances comparable to the dimensions of an atom Atom (order theory), in mathematics Atomic (coffee machine), a 1950s stovetop coffee...

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...

orthogonality in a component-based system Atomicity, in order theory; see Atom (order theory) Atom (disambiguation) This disambiguation page lists articles...

valence bond theory cannot explain. In molecular orbital theory, electrons in a molecule are not assigned to individual chemical bonds between atoms, but are...

An exotic atom is an otherwise normal atom in which one or more sub-atomic particles have been replaced by other particles.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

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

Atomism or social atomism is a sociological theory arising from the scientific notion atomic theory, coined by the ancient Greek philosopher Democritus...

A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral hydrogen atom contains a single positively charged proton in the...

of the dissociated atoms combine to give individual chemical bonds when a molecule is formed. In contrast, molecular orbital theory has orbitals that cover...

dark energy, called phantom dark energy theories, suggest that ultimately galaxy clusters, stars, planets, atoms, nuclei, and matter itself will be torn...

hydrogen atom, the quantum harmonic oscillator and the particle in a box, are too idealized to adequately describe most systems. Using perturbation theory, we...

In first-order logic, a first-order theory is given by a set of axioms in some language. This entry lists some of the more common examples used in model...

hyperfine splitting in the hydrogen atom. Despite the simpler notation, perturbation theory applied to quantum field theory still easily gets out of hand....

history of molecular theory traces the origins of the concept or idea of the existence of strong chemical bonds between two or more atoms. A modern conceptualization...

atoms. Aczel's anti-foundation axiom implies that there is a unique Quine atom. Other non-well-founded theories may admit many distinct Quine atoms;...

composed of atoms. The structure of the atom was discussed, and by the end of the century the leading model: 175  was the vortex theory of the atom, proposed...

In chemistry, bond order is a formal measure of the multiplicity of a covalent bond between two atoms. As introduced by Gerhard Herzberg, building off...

atoms. Caloric theory – the theory that a self-repelling fluid called "caloric" was the substance of heat. Rendered obsolete by the mechanical theory...

phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, specifically in solids and some liquids...

in first- and second-order perturbation theory to account for the first- and second-order Stark effect. Let the unperturbed atom or molecule be in a g-fold...

valence bond theory. In the molecule H 2, the hydrogen atoms share the two electrons via covalent bonding. Covalency is greatest between atoms of similar...

atom induce a corresponding redistribution of electrons in other atoms, such that the electron motions become correlated. While the detailed theory requires...

tight binding theory, also known as the Finnis-Sinclair model. These models are particularly appropriate for metallic systems. Embedded-atom methods are...

of every atom of that element. The atomic number can be used to uniquely identify ordinary chemical elements. In an ordinary uncharged atom, the atomic...