Question

Atomic mass of an element is:
(A) Actual mass of one atom of the element
(B) Relative mass of an atom of the elements
(C) Average mass of an atom of different atom of the element
(D) Always a whole number

Answer 1

It is a definition based question. Atomic mass can also be referred to as atomic weight. This about what a mass of an element could be and compare it with the options given in the question to get the correct option.

Complete Step by Step Solution:
A. Actual mass of an atom of the element is equal to ${m_a} \times 1.66 \times {10^{ - 24}}gm$
Where,
${m_a}$ is the atomic mass of the element.
Therefore, (A) cannot be the correct option.
B. Relative mass of an atom of the elements is defined as the weight in grams of the number of atoms of the elements contained in 12 gm of carbon-12.
C. Average mass of an atom of different atoms is called the atomic mass of an element. We need to take the average mass of different atoms because all the elements have different isotopes.
D. Always a whole number: Atomic mass of an element is not a whole number because it contains isotopes for example, chlorine has two isotopes $_{17}^{35}Cl$ and $_{17}^{37}Cl$ with neutral abundances in the approximate ratio $3:1$. Hence, the average atomic mass of chlorine is approximately $35.5\,g/mol.$

**Therefore, from the above explanation the correct option is (C) Average mass of an atom of different atom of the element

Note:**
Definition based questions are memory based questions. You need to know the definition to know the answer. But for this particular question, if you have the basic idea about atomic mass then also you could solve it as the other options were easy to figure out that they are incorrect. Sometimes it is better to check which options are wrong if you can’t figure out which option is correct.