Question

(a) Explain Pauling method to determine ionic radii?
(b) Describe how noble gases are isolated from air by Ramsey-Raleigh method?

Answer 1

(a) Explain Pauling method to determine ionic radii
Consider a crystal AB with $A^{+}$ cation and $B^{-}$ anion.
The internuclear distance between cation and anion is d. $r^{+}$ and $r^{-}$ are the radii of cation and anion.
$d=r^{+}+r^{-}$.....(1)
$Z^{+}$ and $Z^{-}$ are the effective nuclear charges of cation and anion.
$\frac{r^{+}}{r^{-}}=\frac{Z^{+}}{Z^{-}}$.....(2)
By knowning d, $Z^{+}$ and $Z^{+}$, we can calculate
$r^{+}$ and $r^{+}$.
(b) Isolation of noble gases from air by Ramsey-Raleigh method.
Air is passed through $KOH$ or soda lime. It is then passed through hot $Cu$ and hot $Mg$.
$KOH$ or soda lime absorbs $C{O}_2$. Hot $Cu$ converts oxygen to $CuO$. Hot $Mg$ converts nitrogen to magnesium nitride.
$2Cu+O_2\to 2CuO$
$3Mg+N_2\to M{g}_3{N}_2$