Chapter 15, Problem 15RQ

To determine

The differences between atomic number and mass number of an atom.

Answer to Problem 15RQ

Atomic number is defined as the number of protons present in the nucleus of an atom while the mass number is the addition of a number of protons and neutrons in the nucleus of an atom.

Explanation of Solution

The table below shows the difference between the mass number and atomic number.

Mass number	Atomic number
Mass number is the total number of protons and neutrons are present in the nucleus of an atom.	It is the number of protons present in the nucleus of an atom.
It is defined as the average weight of an element.	It decides the total number of nucleons in atoms nucleus.
Classification and identification of element cannot be decided by mass number.	Atomic number is used in arranging the elements in the modern periodic table and hence used in identification and classification of elements.
It is mostly measured in term of an atomic unit, that is amu.	It is just a numeral value of the protons in the nucleus.

Conclusion:

Therefore, atomic number is defined as the number of protons present in the nucleus of an atom while the mass number is the addition of a number of protons and neutrons in the nucleus of an atom.