Explain with examples $(i)$ Isotopes and $(ii)$ Isobars. Give any two uses of isotopes.

(N/A) $(i)$ Isotopes: These are atoms of the same element having the same atomic number,but different mass numbers. For example,chlorine has two isotopes with atomic number $17$ but mass numbers $35$ and $37$ represented by $_{17}^{35}Cl$ and $_{17}^{37}Cl$.
$(ii)$ Isobars: These are atoms of different elements having the same mass number,but different atomic numbers. For example,Neon $(Ne)$ has atomic number $10$ and Sodium $(Na)$ has atomic number $11$,but both have a mass number of $22$,represented by $_{10}^{22}Ne$ and $_{11}^{22}Na$.
Two uses of isotopes:
$\to$ One isotope of Uranium is used as a fuel in nuclear reactors.
$\to$ One isotope of Cobalt is used in the treatment of cancer.