The atomic species A and B have different number of protons but the same number of nucleons. On the other hand, the atomic species X and Y have the same number of protons but different number of nucleons. Which pair is an example of isobars? Why?

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

(i) or (ii)

Three different atoms of oxygen are represented as:

(i) What do the subscripts (lower figures) and superscripts (upper figures) represent?

(ii) What factor is responsible for the change in the superscripts 16, 17 and 18, though the element is the same?

(iii) What is the usual name for such atoms of an element?

(iv) Give the nuclear composition of

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

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 pair is are isobars?

(i)

(ii)

Give reasons for your choice.