What does relative atomic mass refer to?

Relative atomic mass is defined as the weighted mean mass of an atom of an element compared to 1/12 of the mass of a carbon-12 atom. This definition takes into account the different isotopes of an element and their relative abundances found in nature.

When calculating the relative atomic mass, the isotopes are considered, and their masses are averaged based on their natural occurrence. Each isotope contributes to the overall mass, weighted according to its abundance. This results in a value that is representative of the element as a whole rather than just a single isotope.

Other options lack this specificity and relevance to the common definition used in chemistry. For example, while comparing to hydrogen may offer a rough idea, it is not the formal standard used in determining relative atomic mass. Similarly, stating it as the average of isotopes does not include the important aspect of weighting based on abundance. Lastly, defining mass in moles does not relate directly to atomic mass as it involves a different measurement, specifically concerning the amount of substance rather than the mass ratio to a standard isotope.