What is the relation between the two species?

Composition of the nuclei of two atomic species ‘X’ and ‘Y’ are given as under

                       X    Y

Protons         6      6

Electrons      6      8

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

Mass number of X = 6 + 6 = 12

Mass number of Y 6 + 8 = 14

Atomic number of  X = 6

Atomic number of  Y = 6

X and Y are isotopes, since both the elements contain equal number of atomic number and different mass number.