Sodium chloride, commonly known as table salt (NaCl), is a solid at room temperature. It is found widely in nature and daily life.
The Crystalline Structure of Sodium Chloride
Sodium chloride exists as a solid due to strong ionic bonds. These bonds form between positively charged sodium ions (Na⁺) and negatively charged chloride ions (Cl⁻). The ions arrange into a highly ordered, repeating three-dimensional crystal lattice. This lattice requires significant energy to overcome the attractive forces holding the ions.
Consequently, sodium chloride exhibits a high melting point, approximately 801°C (1474°F). The rigid nature of this ionic lattice also contributes to its characteristic brittleness. When subjected to force, layers of ions can shift, bringing ions of like charge into proximity. This repulsion between similarly charged ions causes the crystal to fracture or break rather than deform.
Sodium Chloride in Different States
Solid sodium chloride does not conduct electricity because its ions are fixed within the lattice. However, when dissolved in water, it dissociates into Na⁺ and Cl⁻ ions. These free-moving ions allow the solution to conduct electricity, making it an electrolyte.
In its molten state, requiring very high temperatures, the rigid lattice breaks down. This frees the ions, allowing them to move freely, making molten sodium chloride an electrical conductor. The ability of sodium chloride to conduct electricity in solution or when molten, contrasting with its non-conductive solid form, highlights the role of mobile ions in electrical flow.
Common Forms and Uses of Sodium Chloride
Sodium chloride is encountered in various common forms, including table salt, rock salt, and sea salt. It is used across many sectors due to its diverse properties. In the food industry, it is widely used as a seasoning to enhance flavor and as a preservative to inhibit microbial growth, thereby extending shelf life.
Beyond food, sodium chloride plays a significant role in industrial applications, such as de-icing roads and sidewalks during colder months. It is also a fundamental raw material in the chemical industry for producing substances like chlorine, sodium hydroxide, plastics, and paper. In medicine, saline solutions, typically 0.9% sodium chloride in water, are routinely used for intravenous therapy, wound cleaning, and as nasal sprays.