Which of the following statements about Rutherford's model of the atom are correct?

Give reasons for the following:
$(a)$ In potassium and calcium,the filling of electrons in the $N$-shell starts after the $M$-shell has acquired $8$ electrons,although the $M$-shell can accommodate up to $18$ electrons. Why?
$(b)$ There is a difference between mass number and atomic mass.

In what way is the Rutherford's atomic model different from that of Thomson's atomic model?

Rutherford designed an experiment to determine the structure of an atom. Answer the following in relation to this experiment:
$(a)$ Name the element he selected for this purpose.
$(b)$ Which subatomic particle was used by him?
$(c)$ What was the drawback of Rutherford's model of the atom?

Write the charge and mass of an electron.

Match the names of the scientists given in column $A$ with their contributions towards the understanding of the atomic structure as given in column $B$.

Column $A$	Column $B$
$(a)$ Ernest Rutherford	$(i)$ Indivisibility of atoms
$(b)$ $J$.$J$. Thomson	$(ii)$ Stationary orbits
$(c)$ Dalton	$(iii)$ Concept of nucleus
$(d)$ Neils Bohr	$(iv)$ Discovery of electrons
$(e)$ James Chadwick	$(v)$ Atomic number
$(f)$ $E$. Goldstein	$(vi)$ Neutron
$(g)$ Mosley	$(vii)$ Canal rays