An Introduction To Barium Iodide
Barium is a group 2 element and Iodine is a group 17 element. This means Barium (Ba) is metal and Iodine is a halogen. Metals and halogens react to form metal halide compounds called salts like Barium Iodide. The chemical formula of Barium Iodide is BaI2. Studying different metal halide compounds helps us in understanding the nature of these two types of element. This is not the only fact that makes Barium iodide interesting. Iodide compounds are important in the field of medicine and also for the manufacture of many organic compounds.
Barium Iodide Structure and Barium Iodide Formula
As mentioned earlier the barium iodide formula is BaI2 r. It exists in two forms-a dihydrate form and an anhydrous form. The dihydrate form of barium iodide is when each barium iodide molecule is observed to be attached to the other 2 water molecules. The chemical formula of dihydrate barium iodide is written as BaI2.2H2O. Anhydrous barium iodide will not have any water molecule attached to itself. We can easily obtain anhydrous barium iodide from dihydrate barium iodide by heating the latter and letting the water molecules evaporate. They are crystalline solids.
The Lewis structure of BaI2 is
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The nature of the bond is ionic.
Structure of Anhydrous Barium Iodide
The anhydrous barium iodide appears as a white odorless powder. Anhydrous barium iodide can exist in 2 different cell structures: A PbCl2 structure and a Fe2P type structure. Pbcl2 is an orthorhombic structure with trigonal prismatic coordination and a sawtooth lattice. In the case of barium iodide barium will be in the middle and iodine on both the sides respectively
Fe2P is a hexagonal structure with a triangular lattice along with a phosphorus atom in the center. In the case of barium iodide, barium will be in the middle.
Chemical Properties of Barium Iodide
Chemical properties of barium iodide can vary slightly between anhydrous barium iodide and dihydrate barium iodide. This is due to the presence of water molecules attached to the barium iodide molecules. This makes the molecule soluble in water, ethanol, and acetone. However in the case of anhydrous barium iodide, although stable salt, it is sensitive to air, light, and moisture. It is also hygroscopic; meaning it will readily absorb water to crystalize into the dihydrate form of barium iodide. Both are sensitive to oxides and are toxic for consumption. As they are metal halide compounds so they are also ionic in nature.
Some Important Reactions Involving Barium Iodide
Barium iodide can be made by the reaction of barium and iodine molecules as metals and halogens are highly reactive. Since iodine is lower in the 17th group, we need to provide heat for the reaction to take place.
Ba + I2 → BaI2
The reaction of potassium iodide with barium nitrate in the presence of water will yield dihydrate barium iodide.
KI(aq) + Ba(NO3)2 (aq) → KNO3 (aq) + BaI2(aq)
This type of reaction is called a double displacement reaction and is reversible.
Because this reaction is done in the presence of water, the formation of barium iodide is followed by water molecules forming ligands of barium iodide, and hence the product which we will get is dihydrate barium hydroxide. Potassium nitrate is water-soluble and hence on heating, we obtain the crystalized anhydrous barium iodide.
The properties and reactions of barium iodide show us why studying this compound is both useful and interesting.
FAQs on Barium Iodide
1. What is the chemical formula and IUPAC name for Barium Iodide?
The chemical formula for Barium Iodide is BaI₂. Its official IUPAC name is simply Barium Iodide. This is because Barium is a Group 2 alkaline earth metal that consistently forms a +2 ion (Ba²⁺), so a Roman numeral to indicate its charge is not necessary, unlike with transition metals.
2. What are the key physical properties of Barium Iodide?
Barium Iodide's physical properties depend on whether it is in its anhydrous or hydrated form:
- Anhydrous Barium Iodide (BaI₂): This form is a white, crystalline solid. It has a molar mass of 391.14 g/mol and a high melting point of 711°C.
- Barium Iodide Dihydrate (BaI₂·2H₂O): This form, which includes two water molecules in its crystal structure, appears as colorless crystals. It has a higher molar mass of 427.17 g/mol and decomposes upon heating.
Both forms are known to be soluble in water and alcohol.
3. What are the important uses of Barium Iodide?
Barium Iodide has several specialised applications in science and industry. Its primary uses include:
- Chemical Synthesis: It acts as a precursor for preparing other iodide compounds and Barium Dioxide (BaO₂).
- Radiation Detection: When doped with Europium, Barium Iodide crystals function as scintillators. These materials emit a flash of light when struck by high-energy radiation, making them essential components in medical imaging devices and nuclear physics research equipment.
- Organic Chemistry: It is occasionally used as a reagent in specific organic synthesis reactions.
4. Is Barium Iodide an ionic or a covalent compound? Explain why.
Barium Iodide (BaI₂) is a classic example of an ionic compound. This is due to the large difference in electronegativity between its constituent elements:
- Barium (Ba) is a metal with very low electronegativity, meaning it readily loses its two outer electrons to form a stable positive ion (a cation), Ba²⁺.
- Iodine (I) is a non-metal with high electronegativity, meaning it readily accepts an electron to form a stable negative ion (an anion), I⁻.
The compound is formed when one Barium atom transfers its two electrons to two Iodine atoms, resulting in a strong electrostatic attraction between the Ba²⁺ cation and the two I⁻ anions.
5. How is Barium Iodide typically prepared?
Barium Iodide is commonly prepared in the laboratory via a neutralisation reaction. One of the most effective methods involves reacting an acid with a base or carbonate. For instance, reacting Barium Carbonate (BaCO₃) with Hydriodic Acid (HI) yields Barium Iodide, water, and carbon dioxide gas.
The chemical equation for this reaction is: BaCO₃(s) + 2HI(aq) → BaI₂(aq) + H₂O(l) + CO₂(g)
The aqueous Barium Iodide solution is then concentrated by evaporation to allow crystals of BaI₂·2H₂O to form.
6. Why is Barium Iodide considered toxic to humans?
The toxicity of Barium Iodide is not due to the iodide ion, but due to the barium ion (Ba²⁺) it releases when dissolved. As a soluble barium salt, it poses a significant health risk if ingested. The Ba²⁺ ions interfere with potassium ion channels in the body's cells, which are vital for nerve impulses and muscle contraction. This can lead to serious conditions like severe hypokalemia (low potassium levels), cardiac arrhythmias, muscle weakness, and even respiratory paralysis. For this reason, it must be handled with strict safety precautions.
7. How does the solubility of Barium Iodide in water compare to Barium Fluoride (BaF₂)?
Barium Iodide (BaI₂) is highly soluble in water, whereas Barium Fluoride (BaF₂) is nearly insoluble. This significant difference is explained by the interplay between lattice energy and hydration energy.
- Lattice Energy: The fluoride ion (F⁻) is much smaller than the iodide ion (I⁻). This allows for a much closer and stronger electrostatic bond with the Ba²⁺ ion in the BaF₂ crystal lattice, resulting in extremely high lattice energy that is difficult for water molecules to break.
- Solubility Trend: Because the lattice energy of BaF₂ is so dominant, it is insoluble. As you move down the halogen group to larger ions (Cl⁻, Br⁻, I⁻), the lattice energy decreases more significantly than the hydration energy, leading to a general increase in the solubility of barium halides.
