Chain reaction

This article is about chain reactions in chemistry and physics. For other uses, see Chain reaction (disambiguation).

A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions.

The neutron-fission chain reaction: a neutron plus a fissionable atom causes a fission resulting in a larger number of neutrons than was consumed in the initial reaction.
Chemical reactions, where a product of a reaction is itself a reactive particle which can cause more similar reactions. For example, every step of H₂ + Cl₂ chain reaction consumes one molecule of H₂ or Cl₂, one free radical H· or Cl· producing one HCl molecule and another free radical.
Electron avalanche process: Collisions of free electrons in a strong electric field forming "new" electrons to undergo the same process in successive cycles.

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