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# Carbon-12? watch

1. What do they mean by 'relative atomic masses are measured on a scale on which the mass of Carbon-12 is exactly 12?

Are they referring to the overall relative atomic mass of carbon or the mass of a single carbon-12 atom? or both...hmmmm
2. they had to standardise on something - because the measured mass wasn't always what you'd naively expect.

the decided to standardise on carbon 12 = relative mass 12
3. (Original post by Miss Understood)
What do they mean by 'relative atomic masses are measured on a scale on which the mass of Carbon-12 is exactly 12?

Are they referring to the overall relative atomic mass of carbon or the mass of a single carbon-12 atom? or both...hmmmm
They are referring to the mass of one carbon-12 atom. All other atoms are measured relative to 12C, the specific isotope.

Logically, by extension, the mass of 1 mole of 12C = 12.00000g
4. (Original post by charco)
They are referring to the mass of one carbon-12 atom. All other atoms are measured relative to 12C, the specific isotope.

Logically, by extension, the mass of 1 mole of 12C = 12.00000g
If carbon - 12 has a mass of exactly 12. Why do we say carbon-12's mass is relative instead of exact.

Why to people refer to the word 'relative atomic mass' when they are just talking about 1 isotope/atom. Surely they should say the 'exact' mass.
5. (Original post by Miss Understood)
If carbon - 12 has a mass of exactly 12. Why do we say carbon-12's mass is relative instead of exact.

Why to people refer to the word 'relative atomic mass' when they are just talking about 1 isotope/atom. Surely they should say the 'exact' mass.
It is chosen as the reference...

you have to first measure the reference and then measure everything else relative to it.

Why else was there a 1 metre lump of iridium/platinum is a case in Paris (now outdated)?

http://en.wikipedia.org/wiki/Metre

or a lump of platinum/iridium metal in a case in Sévres France

http://en.wikipedia.org/wiki/Kilogram

Read and think...

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