Why is NaCI a heterogeneous mixture?

NaCl, or table salt, is not a heterogeneous mixture; it is a homogeneous compound made up of sodium and chloride ions. However, if you're referring to a mixture of NaCl with other substances, such as sand or sugar, that would be considered heterogeneous because the different components can be physically distinguished and are not uniformly distributed. In a heterogeneous mixture, the individual components retain their properties and can be separated by physical means.