Dictionary > Unified atomic mass unit

Unified atomic mass unit

Definition
noun, plural: unified atomic mass units
One twelfth the mass of a neutral atom of the most abundant isotope of carbon (carbon-12)
Supplement
The unified atomic mass unit (u) refers to the 1/12 (0.0833) the mass of the carbon-12 atom. It is used to express the mass of atomic and subatomic particles.
It is also called dalton, named after John Dalton. John Dalton proposed in 1803 to use the mass of hydrogen atom as the natural unit for relative atomic mass. The hydrogen was replaced later on with oxygen. Wilhelm Ostwald suggested to base the relative atomic mass in terms of 1/16 mass of oxygen in 1903. Thus, formerly, the atomic mass unit is based on oxygen. Years later (in 1929), isotopic oxygen was discovered and as such it resulted in the divergence in relative atomic mass representation. The divergence could result in errors. To prevent this, carbon-12 was eventually used as the reference standard in 1961.
At this point in time, the atomic mass unit is based on carbon-12. In so doing, it was called unified atomic mass unit. Nevertheless, the term atomic mass unit without the unified is still being used today although it is no longer based on oxygen-16 but on carbon-12.
Symbol(s):

  • u
  • Da

Synonym(s):

  • dalton
  • atomic mass unit (AMU)


  • You will also like...

    Chromosomes X and Y and Sex Determination
    Chromosomes X and Y and Sex Determination

    This tutorial looks at sex determination via the sex chromosomes, X and Y. Read it to get more info on X and Y chromosom..

    Sugar Homeostasis
    Sugar Homeostasis

    The blood sugar level is regulated by two hormones. The mechanism behind this type of negative feedback control is descr..

    Genetics – Lesson Outline & Worksheets
    Genetics – Lesson Outline & Worksheets

      Topics Modules Quizzes/Worksheets Description Introduction to Genetics Genetics – Definition: Heredity and ..

    Lights' Effect on Growth
    Lights’ Effect on Growth

    This tutorial elaborates on the effect of light on plant growth. It describes how different plants require different amo..

    Still Water Community Plants
    Still Water Community Plants

    This tutorial looks at the adaptations of freshwater plants for them to thrive in still water habitats. Familiarize your..

    Stem
    Stems

    Stems primarily provide plants structural support. This tutorial includes lectures on the external form of a woody twig ..

    Related Articles...

    No related articles found

    See all Related Topics