The chemical formula for strontium chloride is \(\text{SrCl}_2\). This inorganic salt is formed from the elements strontium and chlorine. It exists as a typical ionic substance, composed of positively and negatively charged particles held together by electrostatic attraction. Strontium chloride has a variety of applications, ranging from consumer dental products to industrial processes. Its predictable chemical behavior makes it a useful source of strontium ions in various settings.
How the Formula \(\text{SrCl}_2\) is Constructed
The specific formula of strontium chloride, \(\text{SrCl}_2\), is a direct consequence of the electrical charges carried by its constituent ions. Strontium (\(\text{Sr}\)) is an alkaline earth metal found in Group 2 of the periodic table. It readily loses its two outermost electrons to form a stable cation with a \(2+\) charge (\(\text{Sr}^{2+}\)).
Chlorine (\(\text{Cl}\)), a halogen from Group 17, is a non-metal that tends to gain one electron, forming an anion with a \(1-\) charge (\(\text{Cl}^{-}\)). For the final ionic compound to be electrically neutral, the total positive charge must exactly balance the total negative charge.
Since the strontium ion carries a \(2+\) charge and the chloride ion carries a \(1-\) charge, two chloride ions are required to combine with a single strontium ion to maintain neutrality. The combination of one \(\text{Sr}^{2+}\) and two \(\text{Cl}^{-}\) ions yields the empirical formula \(\text{SrCl}_2\).
Defining Physical Characteristics
Strontium chloride typically presents as a white, crystalline solid, which is characteristic of many ionic salts. The compound is highly soluble in water, dissolving readily to form neutral aqueous solutions that separate into its component ions. This high solubility is a significant factor in many of its applications.
The substance can exist in different hydration states, which affects its physical properties. The anhydrous form, pure \(\text{SrCl}_2\), has a high melting point (around 874 °C) and a density of approximately 3.05 grams per cubic centimeter.
It is most commonly encountered as the hexahydrate, \(\text{SrCl}_2 \cdot 6\text{H}_2\text{O}\), which incorporates six water molecules into its crystal lattice. The hexahydrate is physically softer, less dense, and possesses a much lower melting point, approximately 61 °C. When heated above this temperature, the hexahydrate begins a process of stepwise dehydration, losing its water molecules until the anhydrous form remains.
Essential Industrial and Consumer Uses
Strontium chloride is widely recognized for its use in consumer health products, particularly in toothpastes formulated to treat dentin hypersensitivity, or sensitive teeth. The compound works by physically blocking the microscopic tubules in the dentin layer of the tooth that lead to the nerve. The strontium ions form a barrier over the exposed dentinal surface, which helps prevent external stimuli like cold or heat from reaching the underlying nerves and causing pain.
The strontium ion is responsible for a brilliant, deep crimson color when heated. This property makes strontium chloride a valued ingredient in the pyrotechnics industry for creating red flares and fireworks. It is also utilized as a raw material for producing other strontium-containing compounds, such as strontium chromate pigments.
In specialized medical fields, strontium chloride is used as a vehicle for the radioactive isotope strontium-89. This radioactive form is administered to patients for palliative care, specifically treating pain associated with bone cancer that has spread to other parts of the body. The chemical structure allows for the safe and effective delivery of this radioisotope to targeted areas in the skeletal system.