''Elements in Periodic Table show periodicity of properties.'' List any four such properties.

Arrange the following elements in the order of their decreasing metallic character: $Na, Si, Cl, Mg, Al$.

Where would you locate the element with electronic configuration $2, 8$ in the Modern Periodic Table?

$(a)$ Identify the element that has two completely filled shells and the number of valence electrons in each are as: $(i)$ $1$,$(ii)$ $2$,$(iii)$ $7$,$(iv)$ $8$. $(b)$ Analyse which amongst them is inert.

Which of the given elements $A$,$B$,$C$,$D$ and $E$ with atomic numbers $2$,$3$,$7$,$10$ and $30$ respectively belong to the same period?

$(a)$ Name the element with atomic number $17$.
$(b)$ To which period does it belong?
$(c)$ To which group does it belong?
$(d)$ Write its electronic configuration.