Question 3: What are isotopes? Explain with examples.

ANSWER

Definition of Isotopes
Nuclei of an element who have same charge number Z but different atomic mass number A are called isotopes.

Explanation: Number of protons (or electron because they are equal) in an atom is called atomic number, denoted by Z. Similarly, combined number of protons and neutron in the nucleus of  an atom is called atomic mass number, denoted by A. It is found that all atoms of an element have the same atomic mass number Z, but elements have atoms which differ in their atomic mass numbers. Such atoms are called isotopes of the element. They basically differ in the number of neutrons in the nucleus.

Chemical properties of all isotopes of an element are same because chemical reactions are due to the interaction of electrons only.

Examples of isotopes: Following are few examples of the isotopes.

1. Isotopes of Hydrogen: Hydrogen has three isotopes.
   • Protium: It has only one proton in the nucleus, represented by ₁H¹.
   • Deuterium: It has one proton and one neutron in the nucleus, represented by ₁H².
   • Tritium: Tritium has two neutron and one proton in the nucleus, represented by ₁H³.
2. Isotopes of Uranium: Uranium has two isotopes (check it).
   • Uranium ₉₂U²³⁵: This isotope of Uranium has 92 protons and 143 neutrons.
   • Uranium ₉₂U²³⁸: This isotope of Uranium has 92 protons and 146 neutrons.
3. Isotopes of Carbon: Carbon has three isotopes.
   • Carbon ₆C¹¹: This isotope of Carbon has 6 protons and 5 neutrons.
   • Carbon ₆C¹²: This isotope of Carbon has 6 protons and 6 neutrons.
   • Carbon ₆C¹³: This isotope of Carbon has 6 protons and 7 neutrons.

This should be remembered that there is no change in the chemical properties Hydrogen, Uranium and Carbon regarding their isotopes.