Why is the average atomic mass of most elements the same in every sample that has been analyzed?

The average Atomic Mass of elements remains consistent across samples because it is calculated based on the weighted average of an element's naturally occurring isotopes and their abundances. Since isotopic ratiOS are generally uniform in nature, the average atomic mass does not vary significantly from one sample to another. Additionally, atomic mass is defined relative to the standard atomic mass unit, allowing for a reliable comparison across different samples. Thus, regardless of where or how a sample is taken, the average atomic mass remains the same.