The atomic number of an element is $17$. Predict $(a)$ its valency,$(b)$ whether it is a metal or non-metal,$(c)$ its relative size with respect to other members of its group. Justify your answer in each case.

Up to which element was the Law of Octaves found to be applicable?

The position of some elements $A, B, C, D, E, F$ and $G$ in the Modern Periodic Table is given as under:

Group $\to$	$16$	$17$	$18$
Period $1$			$A$
Period $2$	$B$	$C$	$D$
Period $3$	$E$	$F$	$G$

$(a)$ In which group are inert elements placed?
$(b)$ What type of ions would $B, C, E,$ and $F$ form?
$(c)$ Which element would have chemical properties similar to $C$?
$(d)$ How many shells would $A$ have?
$(e)$ What is the similarity between $A$ and $D$?
$(f)$ Identify the most abundant element in the earth's crust.

The elements $A$,$B$,$C$,$D$,and $E$ have atomic numbers $9$,$11$,$17$,$12$,and $13$ respectively. Which pair of elements belongs to the same group?

Atomic numbers of a few elements are given below: $10, 20, 7, 14$.
$(a)$ What would be the electronic configuration for each of these elements?
$(b)$ Determine the valency of these elements.

The electronic configuration of an element $X$ is $2, 8, 8, 2$. To which $(a)$ period and $(b)$ group of the modern periodic table does $X$ belong? State its valency. Justify your answer in each case.