What are interhalogen compounds?

A compound is said to be an interhalogen compound if its molecule consists of two or more two halogen atoms separately with no other atoms belonging to any group of elements. The most common one that existed is a binary form which consists of a combination of two halogens. Halogens, however, are elements in the periodic table and consist of Fluorine denoted by F, chlorine with the symbol Cl, bromine denoted by Br, iodine by I, and another the astatine which is represented by the symbol At. One more element named Tennessine and denoted by Ts which is created artificially may also be considered a halogen. This is Group 17 of the modern Periodic table. The word halogen has a meaning which suggested salt-producing. The halogens are allowed to react with metals for producingvarious salts, some of which are common sodium chloride (table salt), calcium fluoride,  potassium iodide, silver bromide, and so on so forth.

Coming to the interhalogen compounds the most commonly found or the most popular ones consist of the bromine trifluoride, also chlorine monofluoride, iodine heptafluoride, then iodine pentafluoride, and many more. The formation of the Interhalogen compounds is usuallydue to the reaction of halogen-group elements with one another leading to a combination of two or more halogens. Binary interhalogen compounds consist of two halogens. The molecule of the interhalogen compound can also be made of more than two elements belonging to group 17.

Forms of Interhalogen compounds

Some of the available or known forms of interhalogen compounds are discussed below:

  1. Diatomic interhalogens are usually represented as AX: Examples are BrCl, BrF, ClF, ICl, IBr, etc.
  2. Tetratomic interhalogens which of AX3type . Some examples are ClF3, BrF3, (ICl3)2
  3. Hexatomical interhalogens which are usually of AX5 type consists of the following examples ClF5, BrF5, IF5,
  4. Octatomical interhalogens: This consists of AX7type which includes IF7 and many others.

The types AX and AX3 of the interhalogen compounds usually take place when there is a reaction between halogens having a quite low difference in electronegativity. For example, in ClF and ClF3 respectively.

The types AX5 and AX7 of the interhalogen compounds,however, are commonly are formed by the interaction between larger atoms of the halogens having low electronegativity and the smaller atoms which have electronegativity oh higher range. This mainly occurs as a large number of the smaller atoms can easily fit in the larger ones. This can also be re-interpreted as the AX5 and AX7 types can be formed when there is an interaction between a large size halogen having high electro positivitywith the smaller size group17 element having lower electro positivity. Some examples of such are the BrF5 and IF7 respectively.  The number of atoms present in the molecule increases when the ratio of the radius of larger halogens and smaller ones increase.

The “A” I each type represents the larger halogen with lower electronegativitywhereas  “X” represents the smaller one which is more electronegative.

How can we calculate the number of particles present in the atom?

One can calculate by using the radius ratio which is defined as the radius of a largerhalogen particle divided by the radius of a smaller halogen molecule. In the case where the radius proportion increases there is an increase in the number of atoms per molecule as well. Therefore, Iodine heptafluoride consists of the largest number of particles per atom as the radius proportion is quite high compared to all other interhalogen compounds.

Preparation steps for obtainingInterhalogen Compounds

For the preparation of the interhalogen compounds, the halogens combine directly with each other forming molecules of the compound or there is an interaction between the elements of Group 17 or halogens with other lower formed-interhalogen compoundsthat can take place only under certain conditions. Let’s take an example, chlorine at 437 K, canundergo a reaction with an equal volume of fluorine leading to the formation ofClF. This is commonly used in manufacturing processes to obtain group 17 fluorides. Some reactions showing the formation of interhalogens are given below:

Cl2 +F2→ 2ClF (This takes place at 473K)

I2 + Cl2→ 2ICl

What are some properties of Interhalogen Compounds

Interhalogen compounds can be found in various states such assolid-state, liquid state, or vapor (gas) state. In the case of chlorine monofluoride,it exists in a gaseous state whereas trifluoride bromine is a solid,and trifluoride iodine is a liquid.However, almost all of these compounds at 298 K usually exist in liquid- solids form (or fluids) and the rest of the gases.

The reason that they are mostly covalent is due to the fact of the less electronegativity distinction that exists in the bonded molecules. Some examples of such which are of a covalent nature are bromine trifluoride, iodine heptafluoride, chlorine monofluoride, etc.

Uses of Interhalogen Compounds

  • These compounds can be used as non-aqueous solvents.
  • They are also used as a catalyst in a number of reactions.