Each element has a characteristic atomic mass. The atoms are extremely small particles and it is very difficult to determine their actual masses. For example, mass of one atom of hydrogen has been found to be `1.66 xx 10^(-24)` . Obviously, such a small mass cannot be determined even with the help of a very sensitive balance. To overcome, this problem, the atomic masses are expressed as relative masses i.e., with reference to mass of a standard atom. In 1961, the International Union of Chemists selected the stable isotope of carbon ( carbon -12) as the standard for comparing the atomic and molecular masses of elements and compounds. The atomic mass of the standard, the isotope carbon-12 of carbon is chosen to be 12. Thus, atomic mass may be defined as the relative mass of an atom of the element as compared to an atom of carbon ( carbon-12) taken as 12.
The relative atomic mass of sodium is

Options

A. the mass of one sodium atom
B. the mass of one sodium ion
C. the mass of one sodium atom compared with one twelfth the mass of one carbon-12 atom
D. the average mass of one sodium atom compared with one twelfth the mass of one carbon-12 atom.

Answer

d