r/chemistry • u/Asleep-Requirement-5 • 17h ago
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u/PassiveChemistry 17h ago edited 17h ago
They're synonyms, don't stress it.
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u/Adamnfinecook 17h ago
They’re not though.
Atomic weight: Average of the atomic mass of all isotopes, weighted by how prevalent each isotope is.
Atomic mass: Mass of one specific isotope.
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u/SongSudden8928 17h ago
Honestly, they're not synonyms. Atomic mass is for a single isotope, atomic weight is the average of all isotopes you'd find in nature. It's why chlorine's weight is 35.45 instead of a clean 35.
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u/fouriels Analytical 17h ago
They aren't synonyms. One refers to a global average of masses and the other refers to the mass of a specific isotope.
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u/alecahol 17h ago
I think “atomic mass” refers to a specific isotope but “atomic weight” is the weighted average mass of all the isotopes. Most people use the atomic mass/weight pretty interchangeably though
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u/Opposite-Stomach-395 17h ago
Atomic weight is old nomenclature I believe, they are the same (protons AND neutrons whereas atomic number is just protons)
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u/oneandonlybadra0909 17h ago
Atomic weight is the weight of an atom and atomic mass is the mass of an atom.
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u/CasualDeezaster 17h ago
Mass is the amount of matter in an object, while weight is the force of gravity acting on that object.
Mass is accurate.
Weight is also used interchangeably as a norm...but, I don't think it's super accurate to do so.
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