Q.13:- Composition of the nuclei of two atomic species X and Y are given as under:

                     X    Y

Protons =    6     6

Neutrons =  6     8

Give the mass numbers of X and Y. What is the relation between the two species? 

Answer:-

Mass number of X = No. of protons + No. of neutron

= 6 +6 = 12

Mass number of  Y = 6 + 8 = 14

The species X and Y are the isotopes because their atomic numbers are same and their mass numbers are different, i.e. and