atomic mass unit: Quick Facts

Written and fact-checked by

The Information Architects of Encyclopaedia Britannica

Facts

Also Known As	AMU • dalton

Photos

Diagram showing three isotopes of carbon: carbon-12, carbon-13, and carbon-14, each with labeled protons, neutrons, and electrons, and their stability or radioactivity.

See All Images →

Topics

atom physical constant atomic mass gravitational constant dielectric constant Planck’s constant Bohr magneton Boltzmann constant universal gas constant Rydberg constant decay constant Solar constant speed of light

Italian physicist Guglielmo Marconi at work in the wireless room of his yacht Electra, c. 1920.

All About Physics Quiz