Question

How do you calculate the atomic mass of carbon?

Answer 1

Hint:. The answer to this question is dependent on the definition of atomic mass of the atom which is given as the atomic mass is the sum of the number of protons and number of neutrons in the nucleus of an atom.

Complete step by step answer:
- In the lower classes of general chemistry, we have studied the general facts of the periodic table which gives the information about the arrangement of elements in the order of their atomic number and also they are written in the symbolic form along with their mass numbers.
- Now, let us see how to calculate this atomic mass number.
- Atomic mass number is nothing but the average weight of all the isotopes of that particular element where the mass of each isotope is multiplied by the abundance of that particular isotope.
- Thus, atomic mass can be calculated using the formula,
Atomic mass = ${{n}_{p}} + {{n}_{n}}$
where, ${{n}_{p}}$ is the total number of protons in the nucleus of atom
and ${{n}_{n}}$ is the total number of neutrons in the nucleus of an atom.
Now, for carbon atom with the atomic number 6 and the symbol $C$, the total number of protons is 6 as the atomic number itself is the number of protons and also the total number of neutrons is 6 and thus substituting this in the above formula, we get
Atomic mass of $C = 6 + 6 = 12amu$
Therefore, the correct answer is atomic mass of carbon is 12 amu

Note: Note that atomic mass number has the unit amu (atomic mass unit) which is the mass exactly equal to one – twelfth the mass of carbon – 12 atoms. It can also be written in the form of Dalton unit denoted by ‘D’.