Explain with examples​

(i) Atomic number​
(ii) Mass number
(iii) Isotopes.
(iv) Isobars
(v) Give any two uses of isotopes.

(i)
The number of protons in one atom of an element is known as atomic number of that element. ​

For example, one atom of helium element has 2 protons in it, so the atomic number of helium is 2. ​

(ii)
The total number of protons and neutrons present in one atom of an element is known as its mass number.​

For example, one atom of helium element contains 2 protons and 2 neutrons, so the mass number of helium is 2+2 = 4​

(iii)
Isotopes are atoms of the same element having the same atomic number but different mass number.
For example, hydrogen${(}^{1}H)$ and deuterium ${(}^{2}H)$ are isotopes.

(iv)
Isobars are the atoms of different elements having different atomic numbers but the same mass number. Isobars have different number of protons in their nuclei but the total number of nucleons (protons + neutrons) in them is the same.​

For example, ${}^{3}He$ (Helium) and ${}^{3}H$ (Tritium) are isobars.​

(v)
The two uses of isotopes are:​

1. Radioactive isotopes (such as Uranium-235) are used as a fuel in nuclear reactors of nuclear power plants for generating electricity ​

2. Radioactive isotopes (such as Cobalt-60) are used in the treatment of cancer.​