Thread: atomic weight/mass

Is there any difference bw atomic mass and atomic weight.

and also difference bw relative atomic mass and standard atomic weight.

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Atomic weight and atomic mass are the same, the former being the old-fashioned and obsolete term.

Relative atomic mass and standard atomic weight probably mean the same thing, unless the author tries to make some obscure distinction of his own.

Note that the atomic mass scale changed a few decades ago. Formerly the reference standard was oxygen = 16. Now the single isotope carbon-14 is the reference. That accounts for the slight differences between old and modern tables.
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w = m * g

Originally Posted by georginho_juventusygr

w = m * g

That does not apply to this question.

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Originally Posted by SteveF

Originally Posted by georginho_juventusygr

w = m * g

That does not apply to this question.

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Euh ... I somewhat remember this. But why?

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Atomic weight or atomic mass is merely a relative measure. Starting 200 years ago, an atom of hydrogen was assigned a "weight" of 1.00 and every other element was given a "weight" relative to hydrogen. (Later, oxygen = 16 became the standard. Now it is carbon-14.)

But regardless of whether we are talking about atomic weight or atomic mass, all values are simply calculated relative to our standard. They are neither true weights nor true masses.

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It’s carbon-12, not carbon-14.

Originally Posted by JaneBennet

It’s carbon-12, not carbon-14.

Agreed.



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and what is atomic mass ratio

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Originally Posted by anand_kapadia

and what is atomic mass ratio

This is just another term for atomic mass, since all values in the table are not true masses but a ratio compared to our standard.

I suppose you can also apply mass ratio to subatomic particles, such as referring to the proton-electron mass ratio.

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