Atomic Mass Chemistry

Scientists succeeded when, through the work of Amedeo Avogadro, they were able to define a relative atomic mass unit and develop a relative scale to determine the relative atomic masses for all the elements.
Many experiments have shown his statement to be workable within 2% and it is now known as Avogadro's Law.
Assuming that hydrogen was the smallest element, the relationship between carbon and hydrogen was used to define a relative atomic mass unit.


Scientists arbitrarily assigned hydrogen the relative atomic mass of 1 amu since it is the smallest element and defined an atomic mass unit "amu" as 1/12 the mass of a carbon atom.


Now, nineteenth century scientists could work with the atomic masses of elements without specialized tools because of a mathematical relationship that led to the creation of a relative unit and scale.
On this scale on, if l oxygen is sixteen times larger than the hydrogen atom of mass 16 amu.
If sodium is twenty three times the mass of hydrogen then its atomic mass is 23 amu and so on.
The masses of all elements were calculated from this relationship.
Thus, creating a relative atomic mass scale.
Today scientists are able to measure the masses of atoms with a more direct approach, but its conclusions are very similar to those proposed by the scientists of the nineteenth century.


The modern definition for an atomic mass unit "amu" is exactly 1/12 the mass of a carbon-12 isotope.