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.

$(a)$ Inert elements (noble gases) are placed in group $18$.
$(b)$ Elements in group $16$ ($B$ and $E$) gain $2$ electrons to form $B^{2-}$ and $E^{2-}$ ions. Elements in group $17$ ($C$ and $F$) gain $1$ electron to form $C^{-}$ and $F^{-}$ ions.
$(c)$ $F$ would have chemical properties similar to $C$ because they belong to the same group $(17)$.
$(d)$ $A$ is Helium $(He)$, which is in period $1$, so it has only $1$ shell ($K$-shell).
$(e)$ Both $A$ and $D$ are inert noble gases belonging to group $18$, meaning they have stable electronic configurations (complete valence shells).
$(f)$ $B$ (Oxygen) is the most abundant element in the earth's crust.