Which of the following pairs are isotopes? Give reasons for your choice: 

(i) ${}_{26}{}^{58}\mathrm{A}, {}_{28}{}^{58}\mathrm{B}$ or (ii) ${}_{35}{}^{79}\mathrm{X}, {}_{35}{}^{80}\mathrm{Y}$.

Three different atoms of oxygen are represented as ${}_8{}^{16}\mathrm{O}, {}_8{}^{17}\mathrm{O} \mathrm{and} {}_8{}^{18}\mathrm{O}$. What do the subscripts (lower figures) and superscripts (upper figures) represent? 

Three different atoms of oxygen are represented as ${}_8{}^{16}\mathrm{O}, {}_8{}^{17}\mathrm{O} \mathrm{and} {}_8{}^{18}\mathrm{O}$. What factor is responsible for the change in the superscripts $16$, $17$ and $18$, though the element is the same?

Three different atoms of oxygen are represented as ${}_8{}^{16}\mathrm{O}, {}_8{}^{17}\mathrm{O} \mathrm{and} {}_8{}^{18}\mathrm{O}$. What is the usual name for such atoms of an element?

Three different atoms of oxygen are represented as ${}_8{}^{16}\mathrm{O}, {}_8{}^{17}\mathrm{O} \mathrm{and} {}_8{}^{18}\mathrm{O}$.  Give the nuclear composition of ${}_8{}^{18}\mathrm{O}$.

Composition of the nuclei of two atomic species A and B is given as under :

                   A       B

Protons:    $18$     $20$

Neutrons:  $22$     $20$

Give the mass numbers of A and B. What is the relation between the two species and which element or elements they represent?

Which of the following pairs are isobars?

(i) ${}_{26}{}^{58}\mathrm{A}, {}_{28}{}^{58}\mathrm{B}$ (ii) ${}_{35}{}^{79}\mathrm{X}, {}_{80}{}^{35}\mathrm{Y}$.

Give reasons for your choice.

$$The number of protons, neutrons and electrons in particles A to E are given below:

Giving reasons, find a pair of isotopes from the above particles.