Definition

1. Noun:
   • A theory in chemistry and physics proposing that all matter is composed of tiny, discrete, indivisible, and indestructible particles called atoms. This is the foundational concept that matter is not infinitely divisible but is made up of fundamental units.
   • A specific theory concerning the internal structure of the atom itself. This refers to models describing the arrangement of subatomic particles (like electrons, protons, and neutrons) within an atom.

Usage Examples

• Noun:
  • Modern chemistry is based on atomic theory.
  • Dalton's atomic theory was a major advancement in science.
  • The development of quantum mechanics revolutionized the atomic theory of structure.

Advanced Usage

• "to hold an atomic theory": To subscribe to or advocate for a theory of matter based on atoms.
  • The ancient Greek philosophers Democritus and Epicurus held atomic theories of the universe.

Variants and Related Words

• Atom (n): The basic unit of a chemical element.
• Atomic (adj): Relating to an atom or atoms.
• Atomism (n): A philosophical theory that physical reality is composed of simple, indivisible particles.

Synonyms

• Theory of atoms
• Atomism (in its philosophical and early scientific context)

Notes on Different Meanings

• The first meaning refers to the general concept that matter is atomic in nature.
• The second meaning refers to specific models (e.g., Rutherford's model, Bohr model, quantum mechanical model) that describe atomic structure.

Noun

1. (chemistry) any theory in which all matter is composed of tiny discrete finite indivisible indestructible particles
   • the ancient Greek philosophers Democritus and Epicurus held atomic theories of the universe
2. a theory of the structure of the atom