Question

LiI= 0.310 nm
LiCl= 0.249 nm
NaI= 0.317
NaCl= 0.279 nm
Suggest why there is such a small difference in internuclear distance between LiI and NaI compared to that between LiCl and NaCl?

Answer 1

Internuclear distance between $LiI$ and $NaI$=$|r_{LaI}-r_{NaI}|=0.007nm$

Internuclear distance between $LiCl$ and $NaCl=|r_{LiCl}-r_{NaCl}|=0.030nm$

now $|r_{LiI}-r_{NaI}|<|r_{LiCl}-r_{NaCl}|$

Since, $r_{I^{-}}>r_{C{l}^{-}}$, the size of $LiI$ and $NaI$ are almost equal but the size of $LiCl$ is smaller than that of $NaCl$.