Barium Iodide

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.

FAQ (Frequently Asked Questions)

1.What are the Physical Properties of Barium Iodide? 

The physical properties can vary slightly between the anhydrous barium iodide and dihydrate barium iodide.  The molar mass of anhydrous barium iodide is 391.136 g/mol. The density is 5.15 g/cm3. The melting point of anhydrous barium iodide is 711o C.  In the case of dihydrate barium iodide, the molar mass will be slightly higher due to the presence of water molecules.

Anhydrous barium iodide is white, dihydrate barium iodide appears as colorless crystals. Since the molecular mass of dihydrate barium iodide is greater than the anhydrous barium iodide further, the density will also be higher in the case of dihydrate barium iodide. Hence the molecular mass is 427.267 g/mol; the density is 5.0 g/cm3. The melting point is also higher and is equal to 740o C. 

2. What are the Uses of Barium Iodide?

Barium iodide is used in the preparation of iodide compounds. It is also used for the preparation of barium dioxide. Barium dioxide is very limited and is only used for the preparation of certain medicines and also for the preparation of many organic compounds. This is also used for the preparation of radioactive barium in-situ which is important in the field of nuclear physics and chemistry. Further europium doped barium iodide could produce high scintillation light yields with better energy yields. Scintillation is a flash of light with an extremely small time interval and is of great use in the field of science.