The p-Block Elements

Interhalogen Compounds

Did you know that there are combinations of halogen compounds as well? They are the interhalogen compounds. They consist of two halogens. In this chapter, we will talk about these compounds, look at their properties and uses. Let us start with what interhalogen compounds are.

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Interhalogen Compounds

We can refer to the Interhalogen Compounds as the subordinates of halogens. These are the compounds having two unique sorts of halogens. For example, the common interhalogen compounds include Chlorine monofluoride, bromine trifluoride, iodine pentafluoride, iodine heptafluoride, etc.

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Types of Interhalogen Compounds

We can divide interhalogen compounds into four types, depending on the number of atoms in the particle. They are as follows:

  • XY Compounds
  • Compounds XY
  • Compounds XY
  • XYCompounds

In these notations, we must understand that “X” is the bigger (or) less electronegative halogen. On the other hand, “Y” represents the smaller (or) more electronegative halogen. We can calculate the number of particles in the atom by the concept of the radius ratio. The formula for the same is as follows:

Radius Ratio = Radius of Bigger Halogen Particle/Radius of Smaller Halogen Molecule

With an increase in the radius proportion, we see that the number of atoms per molecule also increases. Therefore, we can make out that Iodine heptafluoride possesses the greatest number of particles per atom. This is because it has a magnificent radius proportion.

Preparation of Interhalogen Compounds

We can manufacture these interhalogen compounds by two main methods. One of them includes the direct mixing of halogens and the other includes a reaction of halogens with the lower Interhalogen compounds.

  • The halogen atoms react to form an interhalogen compound. One example includes the reaction when a volume of chlorine reacts with an equal volume of fluorine at 473K. The resultant product is chlorine monofluoride.
  • In other cases, a halogen atom acts with another lower interhalogen to form an interhalogen compound. For example, fluorine reacts with iodine pentafluoride at 543K. This gives rise to the compound of Iodine Heptafluoride.

Properties of Interhalogen Compounds

  • We can find Interhalogen compounds in vapour, solid or fluid state. A lot of these compounds are unstable solids or fluids at 298K. a few other compounds are gases as well. As an example, chlorine monofluoride is a gas. On the other hand, bromine trifluoride and iodine trifluoride are solid and liquid respectively.
  • These compounds are covalent in nature. We can attribute it to the lesser electronegativity between the bonded molecules. Examples include Chlorine monofluoride, Bromine trifluoride and Iodine heptafluoride. These compounds are covalent in nature.
  • These interhalogen compounds are diamagnetic in nature. This is because they have bond pairs and lone pairs.
  • Interhalogen compounds are very reactive. One exception to this is fluorine. This is because the A-X bond in interhalogens is much weaker than the X-X bond in halogens, except for the F-F bond.
  • We can use the VSEPR theory to explain the unique structure of these interhalogens. In chlorine trifluoride, the central atom is that of chlorine. It has seven electrons in its outermost valence shell. Three of these electrons form three bond pairs with three fluorine molecules leaving four electrons.

Common Shapes of these Compounds

Applying the VSEPR theory, we can see that it forms a trigonal bipyramid. The lone pairs take up the tropical positions. On the other hand, bond pairs take up the other three positions. The axial bond pairs bend towards the tropical position. This happens in order to minimize the repulsions that happen due to lone pair-lone pair bonds. Thus, it has the shape of a bowed T.

interhalogen compounds

Chlorine Pentafluoride

Let us now take the case of Iodine Pentafluoride. The central atom in Iodine pentafluoride is the iodine atom. It has one lone pair and five bond pairs. This is the reason it has a square pyramidal shape. Similarly, let us consider the case of Iodine heptafluoride. It has seven bond pairs and has the shape of pentagonal bipyramid.

Uses of Interhalogen Compounds

  • We use interhalogen compounds as non-watery solvents.
  • Also, we use these compounds as a catalyst in a number of reactions.
  • We use UF6 in the enrichment of 235U. We can produce this by using ClF3 and BrF3.

U(s)     +      3ClF3(l)    →     UF6(g)    +    3ClF(g)

  • We use these compounds as fluorinating compounds.

Solved Examples for You

Q1: Can fluorine ever be a central atom?

Ans: Fluorine cannot be a central particle in the inter-halogen compounds. This is because it is an element from the 2nd period in the periodic table. Since it has 7 valence electrons, it can form only one bond.

Q2: Why can’t hydrogen be the central atom?

Ans: Hydrogen can’t be the central atom. We can attribute this to the fact that an atom will always attempt and get to the condition of most minimal energy. In case of Hydrogen, this means it can form only a single bond. It also has a very small size and does not fit into the other molecules present around it.

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