Why Is Carbon Listed as 12.0107 g/Mole?

  • Thread starter pivoxa15
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In summary, the weight of carbon listed in the table of elements is 12.0107g/mole, which includes all types of carbon found in nature. This is different from the 12g per mole definition of Carbon-12, which is only referring to the specific isotope. This suggests that there are more heavier isotopes of carbon than lighter ones in nature. The atomic mass unit (a.m.u.) is a unit of mass, while relative atomic mass (r.a.m.) is related to the proportion of isotopes. The conversation also mentions that the a.m.u. is the mass of a nucleon, not the entire atom.
  • #1
pivoxa15
2,255
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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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  • #2
No, the mole was defined to be 12g of the Carbon-12 isotope, not of the naturally occurring isotope mix.
 
  • #3
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.
 
  • #5
the amu of an atom is an average of the most common occurring isotopes
 
  • #6
Huh? A.m.u. is a unit of mass.
 
  • #7
Rach3 said:
Huh? A.m.u. is a unit of mass.

umm...ya, thus, atomic mass unit :smile:
 
  • #8
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.
 

1. What is the significance of carbon being listed as 12.0107 g/mole?

Carbon's atomic mass is listed as 12.0107 g/mole because it is the weighted average of all naturally occurring isotopes of carbon. This means that a mole (6.022 x 10^23) of carbon atoms has a mass of 12.0107 grams.

2. Why is carbon's atomic mass listed with so many decimal places?

The atomic mass of an element is determined by the mass of its isotopes and their relative abundance. Carbon has several isotopes with slightly different masses, which is why its atomic mass is listed with so many decimal places to accurately reflect the average mass of a carbon atom.

3. How was the atomic mass of carbon calculated?

The atomic mass of carbon was calculated by taking the weighted average of the masses of its naturally occurring isotopes. This is done by multiplying the mass of each isotope by its relative abundance and then summing the values.

4. Why is carbon's atomic mass not a whole number?

Since carbon has several isotopes with different masses, its atomic mass is not a whole number. The decimal value represents the average mass of all the isotopes present in nature.

5. Does the atomic mass of carbon ever change?

No, the atomic mass of an element is constant and does not change. However, the atomic mass listed on the periodic table may change slightly due to new discoveries of isotopes or more precise measurements of relative abundance.

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