Unified atomic mass, also known as atomic mass unit (amu) or Dalton (Da), is a unit of mass commonly used in chemistry and physics to express the mass of atomic and subatomic particles. It is defined as 1/12th the mass of an atom of carbon-12, which is assigned a mass of exactly 12 atomic mass units.
The concept of unified atomic mass is based on the relative masses of different atoms and particles compared to the carbon-12 atom. For example, an atom of hydrogen has a mass of approximately 1 atomic mass unit, while an atom of oxygen has a mass of approximately 16 atomic mass units.
The use of unified atomic mass allows scientists to express the masses of atoms and molecules in a convenient and standardized manner. It provides a relative scale for comparing the masses of different atoms and calculating molecular masses. This unit is particularly useful in the field of chemistry when determining the stoichiometry of chemical reactions and calculating the proportions of elements in compounds.