Question

Mass number is denoted by
a) $D$
b) $S$
c) $A$
d) $Z$

Answer 1

The mass number of an element can tell us about the number of protons and neutrons and could tell us if the atom is radioactive or not.
Different isotopes of an atom could have different mass numbers based on their changed number of protons.

Complete step-by-step answer: We all know that most of the space in an atom is empty and the mass of the elements are concentrated in their nucleus. And so the mass number of an element is solely dependent on the composition of the nucleus of that atom. Which means that the mass number would depend on the number of protons and the number of neutrons which are present in the nucleus of that atom. Together, the protons and the neutrons are termed as the nucleons. Therefore, the mass number of an atom can be defined as the sum of the number of protons and the number of neutrons which are present in the nucleus of the atom. For instance, the mass number of the atom oxygen is $16$ because it has the number of protons $8$ which is equal to the number of neutrons $8$. So, the calculation of the mass number of the atoms can be done by the following equation,
$MassNumber=numberOfprotons+NumberOfNeutrons=NumberOfNucleons$
Here, we have written the equation of mass number, but we could use the symbols to represent each of them.
So, the symbol of mass number is $A$ and that to protons and neutrons could be $p$ and $n$ or $\upsilon$ respectively. So, this equation could be written as,
$A=p+n$
Now, if we consider the options given in the question we can see that the option C is the most appropriate answer.

So, the correct option would be option c.

Note: The mass number of an atom is the sum of the protons and the neutrons or the nucleons. And the symbol which is used for representation of the mass number is $A$.