Question

Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes, and (iv)Isobars. Give any two uses of isotopes.

Answer 1

Hint: In order to answer this question, one must have a clear idea about the structure of the atom and the various parameters related to it. An atom of any element has a fixed atomic number and mass number. An element can also have various isotopes and isobars (compared to the other species).

Complete step by step solution:
In this question, we have asked about
(i) Atomic number: The atomic number is the total number of protons present in the atom. For example, the atomic number of $Mg$ is $12$. It contains $12$ protons and $12$ electrons.
(ii) Mass number: It is the sum of the number of neutrons and the number of protons. For example, the atomic number of Lithium is $4$ which is equal to the number of protons, the number of neutrons of magnesium is $4$. The mass number is equal to $8(4+4)$.
(iii) Isotopes are the elements having the same atomic number but different mass numbers. They have the same chemical properties as the number of valence electrons is the same. For example, ⁶C₁₂, ⁶C₁₃, ⁶C₁₄ are the three isotopes of carbon. They have the same atomic number but different mass numbers due to the difference in the number of neutrons.
(iv) Isobars are elements having the same mass number but different atomic numbers. For example. ¹⁸Ar₄₀,¹⁹K₄₀ are isobars having the same atomic mass but different atomic numbers.
The two uses of isotopes are:
(i) As nuclear fuel: An isotope of uranium $(U – 235)$ is used as a nuclear fuel.
(ii) An isotope of cobalt is used in the treatment of cancer.

Note:
In short, Mass number is the number of nucleons, i.e., number of protons and neutrons. When two different elements have the same mass number, they are called isobars. When two atoms have the same atomic number but the different mass numbers, they are called isotopes of each other.