atomicity

Atomicity refers to the quality of being an atom or of existing as a single, indivisible unit within a given context. The term is used across disciplines to denote something that cannot be meaningfully subdivided in that context.

In chemistry, atomicity describes the number of atoms that constitute a molecule or a cluster. Monatomic elements consist of single atoms, such as helium and neon. Diatomic molecules contain two atoms of the same element, such as O2 and N2. Polyatomic molecules consist of three or more atoms, like water (H2O) or methane (CH4). The concept serves to classify substances and to predict bonding and properties.

In physics and the history of science, atomicity has referred to the idea that matter is composed of indivisible units called atoms. While classical ideas treated atoms as indivisible, modern physics recognizes subatomic particles, yet the term is still used in a general sense to denote a basic, discrete unit of matter.

In computer science, atomicity is a correctness property of operations and transactions. An atomic operation or transaction appears indivisible: its effects are applied completely or not at all. Atomicity is one of the ACID properties of database transactions and is also implemented in concurrent programming through atomic instructions, locks, and memory transactions to prevent partial updates.

In distributed systems, atomicity across multiple nodes is often simulated with protocols that commit or abort changes collectively, since true global atomicity is difficult to achieve in asynchronous environments.