What does the term relative atomic mass (Aᵣ) refer to?

The term relative atomic mass (Aᵣ) specifically refers to the average mass of an atom of an element compared to one-twelfth of the mass of a carbon-12 atom. This means that Aᵣ is a dimensionless quantity that reflects how much heavier or lighter an atom is compared to the standard reference isotope, which is carbon-12.

One key aspect of Aᵣ is that it takes into account the natural abundance of all isotopes of an element and their respective masses. Therefore, when calculating the relative atomic mass, it is not simply the mass of a single atom, but rather an averaged value that represents all occurrences of that element in nature. This approach allows chemists to use a standard comparison point (carbon-12) to provide a consistent measure across different elements.

The other choices do not capture the specific meaning of relative atomic mass correctly. For example, while one might think of the mass of an atom in grams, relative atomic mass is not expressed in grams but rather as a ratio relative to carbon-12. Similarly, while the weight of an atom could imply some measurement, it does not convey the concept of a relative comparison to a standard. Finally, the combined mass of protons and