Find out the valency of an element $X$ having atomic number $16$.

Dalton's atomic theory successfully explained which of the following laws?
$(i)$ Law of conservation of mass
$(ii)$ Law of constant composition
$(iii)$ Law of radioactivity
$(iv)$ Law of multiple proportion

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 ...........

$(a)$ Which popular experiment is shown in the figure?
$(b)$ List three observations of this experiment.
$(c)$ State conclusions drawn from each observation of this experiment.
$(d)$ State the model of atom suggested on the basis of the above experiment.

Write down the electron distribution of chlorine atom. How many electrons are there in the $L$ shell? (Atomic number of chlorine is $17$).

Give the salient features of Rutherford's nuclear model of the atom.