The unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic masses and molecular masses. It is defined to be 1/12 of the mass of one atom of carbon-12. 1 u = 1/NA gram = 1/(1000 NA) kg   (where NA is Avogadro's number) 1 u ≈ 1.66053886 × 10−27 kg See 1 E-27 k ...

Including:

• Atomic mass unit - Measuring relative atomic masses
• Atomic mass unit - History

Read more here: » Atomic mass unit: Encyclopedia - Atomic mass unit

The relative atomic mass is measured with a mass spectrometer. After placing a sample of the element to be measured in the mass spectrometer it is bombarded with electrons which turns the atoms into positive ions. An electric field is then used to accelerate these positive ions, after which the ions are deflected using a magnetic field. As a result the various isotopes are separated out due to the ions of lighter isotopes being deflected more than those heavier. This produces a mass spectrum. This spectrum provides two things: Relative iso ...

See also:

Atomic mass unit, Atomic mass unit - Measuring relative atomic masses, Atomic mass unit - History

Read more here: » Atomic mass unit: Encyclopedia II - Atomic mass unit - Measuring relative atomic masses