Instead of using the atomic mass, the property that is now commonly used to characterize elements is the relative atomic mass, also known as the atomic weight.
The relative atomic mass is a dimensionless quantity that compares the mass of an atom of a particular element to the mass of an atom of carbon-12. Carbon-12 isotope is chosen as the reference because it is abundant and has a well-defined atomic mass of exactly 12 atomic mass units (u).
The relative atomic mass is determined by considering the masses and abundances of the various isotopes of an element. Since different isotopes of an element have different masses due to varying numbers of neutrons, the relative atomic mass is calculated as a weighted average of the isotopic masses, taking into account their natural abundances.
For example, the relative atomic mass of carbon is approximately 12.01. This value takes into account the masses and abundances of carbon-12, carbon-13, and carbon-14 isotopes, reflecting their relative contributions to the overall atomic mass of carbon.
The use of relative atomic mass provides a standardized way of comparing the masses of different elements and allows for more accurate and precise measurements and calculations in chemistry and physics. It is a more practical and convenient property than the absolute atomic mass for many applications.