Why Is Carbon Listed as 12.0107 g/Mole?

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The discussion centers on the atomic weight of carbon, specifically the value of 12.0107 g/mole. This figure reflects the average atomic mass of all naturally occurring carbon isotopes, rather than solely the Carbon-12 isotope, which is defined as having a mass of exactly 12 g/mole. The presence of heavier isotopes, such as Carbon-13 and Carbon-14, contributes to this average. Participants clarify that the atomic mass unit (a.m.u.) is a unit of mass for nucleons, while relative atomic mass (r.a.m.) considers the proportions of isotopes in nature, leading to the confusion in terminology. The discussion highlights the distinction between the definition of the mole in relation to Carbon-12 and the average atomic mass of carbon as found in nature.
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In my table of elements, C is listed as having a weight of 12.0107. I presume it means 12.0107g/mole of carbon. I thought Carbon was defined to be 12g per mole?
 
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No, the mole was defined to be 12g of the Carbon-12 isotope, not of the naturally occurring isotope mix.
 
Rach3 said:
No, the mole was defined to be 12g of the Carbon-12 isotope, not of the naturally occurring isotope mix.

So that weight of C was taken as all types of carbon in nature, not just the 12 isotope. It would also suggest there are more heavier isotopes of carbon than lighter ones in nature.
 
the amu of an atom is an average of the most common occurring isotopes
 
Huh? A.m.u. is a unit of mass.
 
Rach3 said:
Huh? A.m.u. is a unit of mass.

umm...ya, thus, atomic mass unit :smile:
 
Yes, but the a.m.u. is the mass of a nucleon. You're confusing it with r.a.m., or relative atomic mass - which is related to the proportion of isotopes, as Rach3 said.
 
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