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:
The relative number and kinds of atoms are varying in a given compound.

The charge on an electron is equal to

Explain the following with one example of each:
$(i)$ Atomic number
$(ii)$ Mass number

Give reasons for the following:
$(a)$ Ions are more stable than atoms.
$(b)$ Noble gases show low reactivity.

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 ...........