who discovered atomic mass

The idea of atomic mass was developed gradually, but the key early figure usually credited is the English chemist John Dalton (around 1803–1808).

Quick Scoop: Who “discovered” atomic mass?

• Dalton was the first to systematically assign relative masses to atoms of different elements, using hydrogen as the lightest reference.

• He didn’t know absolute masses in grams; instead, he created a relative atomic weight scale , which is the conceptual ancestor of today’s atomic mass values on the periodic table.

• Later scientists refined and formalized this:
  • Stanislao Cannizzaro used Avogadro’s ideas in the mid‑1800s to clean up and standardize atomic masses for many elements.

* **Francis Aston** (early 1900s) used the mass spectrograph to measure atomic and isotopic masses much more precisely.

So if you’re answering a textbook or exam‑style question “Who discovered atomic mass?” the expected name is almost always John Dalton , while recognizing that modern atomic mass is the result of a long chain of contributions.

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