The atomic mass of an element is related to the mass of carbon-12 (C-12) through the concept of the atomic mass unit (amu). The atomic mass unit is defined as 1/12th of the mass of a carbon-12 atom.
To determine the atomic mass of an element, scientists compare it to the mass of a carbon-12 atom. This is done by measuring the relative mass of the element's atoms compared to carbon-12.
For example, let's consider oxygen (O). The atomic mass of oxygen is approximately 16.00 amu. This means that, on average, an oxygen atom is approximately 16 times heavier than 1/12th of a carbon-12 atom.
The atomic mass of an element takes into account the different isotopes of that element and their relative abundances. Isotopes are atoms of the same element with different numbers of neutrons, resulting in different atomic masses. By considering the average atomic mass of all the naturally occurring isotopes of an element, scientists can calculate its atomic mass.
In summary, the atomic mass of an element is determined by comparing the mass of its atoms to the mass of a carbon-12 atom, which is taken as the reference point with a mass of approximately 12 atomic mass units.