Final answer:
D. NaCl is a heterogeneous mixture. The incorrect statement in the provided list is 'NaCl is a heterogeneous mixture,' as sodium chloride (NaCl) is a homogenous, crystalline compound, not a mixture.
Step-by-step explanation:
The student has presented a set of statements regarding sodium, chlorine, and sodium chloride, with the task of identifying which statement is not correct. Analyzing the given options, we find that:
- Sodium and chlorine are elements,
- Sodium chloride is a compound,
- Sodium chloride is a pure substance,
- NaCl is a heterogeneous mixture - This statement is incorrect as NaCl (sodium chloride) is not a heterogeneous mixture but is instead a homogeneous substance that forms a crystalline structure.
- NaCl added to water forms a pure solution.
NaCl is a compound formed from sodium and chlorine, and it has distinct properties different from its constituent elements. It forms ionic bonds between sodium cations and chloride anions, resulting in a stable crystalline lattice that is uniform throughout, making it a homogeneous substance. Therefore, the incorrect statement among the options given is that 'NaCl is a heterogeneous mixture'.