Question

Why are the atomic masses based on carbon 12 as standard?

Answer 1

Hint: Carbon-12 is the more abundant of the two stable isotopes of carbon (the other is carbon-13), accounting for $98.93\mathrm{\%}$ of the element. The triple-alpha mechanism, which creates it in stars, is responsible for its abundance. Carbon-12 is particularly important because it serves as the reference point for determining the atomic masses of all nuclides; the atomic mass is, by definition, precisely 12 daltons. Carbon-12 has six protons, six neutrons, and six electrons.

Complete answer:
Carbon-12 is the more abundant of the two stable isotopes of carbon (the other is carbon-13), accounting for $98.93\mathrm{\%}$ of the element. The triple-alpha mechanism, which creates it in stars, is responsible for its abundance. Carbon-12 is particularly important because it serves as the reference point for determining the atomic masses of all nuclides; the atomic mass is, by definition, precisely 12 daltons. Carbon-12 has six protons, six neutrons, and six electrons.
The mass of an atom is its atomic mass. At rest, 1 dalton equals 12 times the mass of a single carbon-12 atom. The nucleus' protons and neutrons account for almost half of an atom's overall mass, with electrons and nuclear binding energy playing a minor role. As a result, when calculated in daltons, the numeric value of the atomic mass is almost equal to the mass quantity.
Since the chemical atomic weights of carbon 12 are almost equal to those of the natural mix of oxygen, it was selected as the standard. Since no other nuclide has an identical whole-number mass on this scale except carbon-12. Six protons, six neutrons, and six electrons make up carbon-12.

Note:
Carbon-12 is the more abundant of the two stable isotopes of carbon (the other is carbon-13), accounting for $98.93\mathrm{\%}$ of the element. The triple-alpha mechanism, which creates it in stars, is responsible for its abundance. Carbon-12 is particularly important because it serves as the reference point for determining the atomic masses of all nuclides; the atomic mass is, by definition, precisely 12 daltons. Carbon-12 has six protons, six neutrons, and six electrons.