Answer
The distance between $Li^{+}$ and $Cl^{-}$ is longer in solid phase than gas phase because in solid phase, all the ions are close to each other. So each $Li^{+}$ ion attracts many $Cl^{-}$ ions and thus the distance between ions increases. Whereas in gas phase, ions are very far from each other, so $Li^{+}$ is more attracted to the $Cl^{-}$ ion it is bonded to and thus the distance is less. The $Li^{+}$ and $Cl^{-}$ ions are much closer to each other in gas phase.
Work Step by Step
The distance between $Li^{+}$ and $Cl^{-}$ is longer in solid phase than gas phase because in solid phase, all the ions are close to each other. So each $Li^{+}$ ion attracts many $Cl^{-}$ ions and thus the distance between ions increases. Whereas in gas phase, ions are very far from each other, so $Li^{+}$ is more attracted to the $Cl^{-}$ ion it is bonded to and thus the distance is less. The $Li^{+}$ and $Cl^{-}$ ions are much closer to each other in gas phase.
