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 ...........

(N/A) The experiment led to the discovery of the atomic nucleus.
$(b)$ Isotopes are atoms of the same element having the same atomic number but different mass numbers.
$(c)$ Neon $(Z=10)$ has an electronic configuration of $2, 8$,so its valency is $0$. Chlorine $(Z=17)$ has an electronic configuration of $2, 8, 7$,so it needs $1$ electron to complete its octet,making its valency $1$.
$(d)$ Silicon $(Z=14)$ has an electronic configuration of $2, 8, 4$. Sulphur $(Z=16)$ has an electronic configuration of $2, 8, 6$.