Relative Atomic Mass 1u: Mass of Carbon-12 Atom & Oxygen-16 Atom

[cks]

1 u = 1/12 of the mass of a neutral carbon atom with nuclear charge 6 and mass number 12,

1 u = 1/12 * 12.000000 /NA * 0.001

where NA is avogadro's number.

I wonder is it that the scientists purposely make one mole of carbon-12 to be just 12.00000g?

I want to ask is it when the relative atomic mass of oxygen-16 is 15.99491, then the mass of the oxygen-16 atom is 15.99491 * 1u.?

 

[f95toli]

Well, Avogadro's number is, by definition, equal to the number of atoms in 12 gram of carbon-12.
So, yes, it is on purpose.

 

[charng]

I can confirm that the relative atomic masses of carbon-12 and oxygen-16 are indeed 12.000000 and 15.99491, respectively. These values are determined through careful experiments and calculations, and they represent the average mass of one atom of each element compared to the mass of one atom of carbon-12.

The reason why carbon-12 was chosen as the standard reference is because it is the most abundant stable isotope of carbon and has a well-defined atomic mass. By setting the mass of one mole of carbon-12 to be 12.00000g, it allows for a more convenient and consistent way of comparing the masses of different atoms.

And yes, the mass of an oxygen-16 atom would be 15.99491 times 1u, or 15.99491u. This is because the relative atomic mass is defined as the mass of one atom of an element in atomic mass units (u).

I hope this explanation helps to clarify any confusion about relative atomic masses and the mass of individual atoms. As scientists, we strive for precision and accuracy in our measurements and calculations, and the use of these standardized values helps us to achieve that.