Question

Which of the following is used as a standard for determination of atomic mass?
A.${O^{16}}$
B.${C^{12}}$
C.${H^1}$
D.${O^{17}}$

Answer 1

The atomic mass of an atom is calculated by the addition of the neutron and the proton of the atom, the atom nuclide which is chosen as a standard atom is because it has a whole number atomic mass.

Complete step-by-step answer: The atomic mass of an element can also be said as a relative atomic mass because it is a ratio of the atomic mass of an atom to some standard atomic mass. Now, the standard unit of atomic mass, since 1961, is selected as a one-twelfth atomic mass of carbon isotopic carbon-12.
Now, an isotope is maybe one, two or three, even more, species of the same atom, which only differ in atomic mass, that is they have a different count of neutrons or protons amongst each other.
Now, since carbon-12 is in abundance and the number of neutrons, a number of protons are exactly equal, that is six Also, they have an atomic mass of the whole number, therefore, it was easy to consider carbon-12 as a standard atom and one-twelfth of the atomic mass of carbon-12 as the standard unit of atomic mass or relative atomic mass.
The essay unit of atomic mass is $1amu$ or dalton.
Hence, carbon-12 is used as the standard to determine the atomic mass.

Note: The atomic mass of an atom is calculated as the total number of the neutron and the proton divided by the atomic mass of the one-twelfth of the carbon-12 atom, and its SI unit is 1amu this is also known as relative atomic mass.