- #1
pivoxa15
- 2,255
- 1
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?
Rach3 said:No, the mole was defined to be 12g of the Carbon-12 isotope, not of the naturally occurring isotope mix.
Rach3 said:Huh? A.m.u. is a unit of mass.
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.
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.
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.
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.
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.