Question

Is sodium chloride a mixture?

Answer 1

Sodium chloride solid is not a mixture. It is a pure substance... It cannot be physically separated into its components, $$Na^{+} $$ and $$ Cl^{-}$$. It would require energy input, and that is clearly not a physical means.

However, if for some reason, you meant NaCl(aq) then sodium chloride in water is a mixture, occurring through the physical dispersion of a liquid solvent amongst the ions, $$Na^{+} $$ and $$Cl^{-}$$ that dissociate in solution, surrounding them to separate them from each other.

This qualifies as a mixture since evaporation allows the reformation of sodium chloride solid again, thus separating the components, $$ NaCl$$ and $$H_{2}O$$ via physical means. It is known as a homogeneous mixture.