Which among the following isoelectronic species has the smallest size?
$O^{2-}, F^{-}, Ne, Na^{+}, Mg^{2+}, Al^{3+}, Si^{4+}$

$A, B, C, D$ and $E$ are elements with atomic numbers $13, 11, 9, 7$ and $16$ respectively. Among these elements,the ion of an element $X$ has the largest size and the ion of an element $Y$ has the smallest size. $X$ and $Y$ are respectively (Assume that all ions have the nearest inert gas configuration).

Which of the following properties displays a progressive increase down a group in the periodic table?

If the interionic distance between $Na^{+}$ and $F^{-}$ ions is $2.31 \ \mathring{A}$,then the radii of $Na^{+}$ and $F^{-}$ are:

What is atomic radius in reality?

The correct order of atomic radii of $N$,$F$,$Al$,and $Si$ is: