Is it possible for the atom of an element to have one electron,one proton,and no neutron? If so,name the element.

Calculate the number of neutrons present in the nucleus of an element $X$ which is represented as $^{31}_{15}X$.

What information do you get from the figure about the atomic number,mass number,and valency of atoms $X$,$Y$,and $Z$? Give your answer in a tabular form.

State whether the following statement is true or false:
Each isotope of an element is an impure substance.

List applications of any three isotopes in various fields.

Fill in the blanks in the following statements:
$(a)$ Rutherford's $\alpha$-particle scattering experiment led to the discovery of the ............
$(b)$ Isotopes have same ............ but different .............
$(c)$ Neon and chlorine have atomic numbers $10$ and $17$ respectively. Their valencies will be ............ and ............. respectively.
$(d)$ The electronic configuration of silicon is .......... and that of sulphur is ...........