What is Sodium Chloride like in gas state? Since sodium chloride is sodium and chlorine atoms bonded as a lattice and there are no discrete molecules, doesn't that mean in gas state, sodium chloride is simply sodium and chlorine atoms separate from each other, resulting in a mixture of sodium gas and chlorine gas?
No, in the gas phase sodium chloride exists as a monomer (the sodium chloride molecule) along with its dimer $\ce{Na2Cl2}$.  The dimer has a roughly rectangular shape and is quite floppy with chlorines located diagonally across from each other.  The dimer makes up about 27% of the mix.  All of the bond lengths, etc. can be found in this thesis.  Go to the end and you'll see the full paper that appeared in JACS with all of the data.