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Interhalogen Compounds

Last Updated : 21 Jul, 2022
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The p-block elements are known to be those elements in which the electron enters in one of the three orbitals of the p-block. There are 6 groups of p-block elements. The properties of p-block elements are that they are shiny and are good conductor of heat and electricity since they have free electrons. Let’s learn about interhalogen compounds,

Interhalogen Compounds

When halogen group elements react with each other, interhalogen compounds are created. In other terms, it’s a molecule made up of two or more distinct group 17 elements. The vast majority of known interhalogen compounds are binary in nature (composed of only two distinct elements). In general, their equations are XYn, where n = 1, 3, 5, or 7, and X is the less electronegative of the two halogens. Because halogens have odd valences, the value of n in interhalogens is always odd. They’re all susceptible to hydrolysis and ionization, resulting in poly halogen ions. Because astatine is extremely radioactive, those created with it have a very short half-life. Interhalogen chemicals are divided into four categories:

  1. Diatomic interhalogens (AX)
  2. Tetratomic interhalogens (AX3)
  3. Hexatomic interhalogens ( AX5)
  4. Octatomic interhalogens (AX7)

Properties of Interhalogen compounds

  1. These molecules are diamagnetic and covalent in nature.
  2. These chemicals form bonds that are more reactive than diatomic halogen bonds.
  3. These molecules’ physical properties are transitional between their constituents.
  4. AX3 molecules have a bent T shape.
  5. AX5 molecules are square or pyramidal.
  6. AX7 molecules have a bipyramidal or pentagonal structure.
  7. The length of the bond is determined by the size of the constituent halogens.
  8. Because of the increase in molecular weight, a molecule made up of lighter group 17 elements is rather colorless, whereas one made up of higher halogens is darker in color.
  9. The greater the difference in electronegativities between the two halogens in an interhalogen, the higher the boiling point of the interhalogen.

Diatomic interhalogens

The physical properties of the interhalogens of form XY are intermediate between those of the two-parent halogens. Because the less electronegative halogen, X, has been oxidized and has a partial positive charge, the covalent link between the two atoms has an ionic nature. All fluorine, chlorine, bromine, and iodine combinations with the above-mentioned general formula are known, but not all of them are stable. Some astatine-halogen combinations aren’t even known, and the ones that  are extremely unstable. The lightest interhalogen chemical, for example, is chlorine monofluoride which is an odorless and colorless gas.

Tetratomic interhalogens

Chlorine trifluoride (ClF3) is a colorless gas that condenses into a green liquid and solidifies into a white solid. It’s created in a nickel tube by reacting chlorine with an excess of fluorine at 250°C. It reacts more violently and explosively than fluorine. The molecule is T-shaped and flat. It is used while producing uranium hexafluoride.

Bromine trifluoride (BrF3) is the yellow-green liquid conducting electricity and self-ionizes into [BrF2]+ and [BrF4]. When it reacts with metals or metal oxides, it does produce comparable ionized entities; while reacting with others, it produces metal fluoride and also free bromine and oxygen. It is utilized as a fluorinating agent in organic chemistry. Its molecular structure is identical to that of chlorine trifluoride.

Under pressure, iodine trichloride (ICl3) forms lemon-yellow crystals that melt into a brown liquid. It can be synthesized from the elements of iodine pentoxide and hydrogen chloride at low temperatures. It forms tetrachloroiodides (ICl4) when it reacts with several metal chlorides and then hydrolyzes in water. Each iodine atom is surrounded by four chlorine atoms in this planar dimer (ICl3)2.

Hexatomic interhalogens

A heavier halogen is coupled with five or seven fluorine atoms in all stable hexatomic and octatomic interhalogens. Fluorine atoms, unlike other halogens, have a strong electronegativity and a tiny size that allows them to be stabilized.

Chlorine pentafluoride (ClF5) is a colorless gas that is created by combining chlorine trifluoride and fluorine at high temperatures and pressures. Water, as well as most metals and nonmetals, reacts aggressively with it. Bromine pentafluoride (BrF5) is a colorless fuming liquid formed by mixing bromine trifluoride with fluorine at 200°C. Although it is physically stable, it reacts severely with water, metals, and nonmetals. Iodine pentafluoride (IF5) is a colorless liquid formed by the reaction of iodine pentoxide with fluorine or iodine with silver(II) fluoride. It has a strong reactivity, even when used with glass. It forms hydrofluoric acid when it combines with water, and iodine heptafluoride when it reacts with fluorine gas. The molecule has a tetragonal pyramid shape.

Octatomic interhalogens

The fluorinating agent iodine heptafluoride (IF7) is a colorless gas. Iodine pentafluoride is created by reacting it with fluorine gas. A pentagonal bipyramid is the shape of the molecule. This is the only interhalogen chemical known in which the bigger atom carries seven smaller atoms. All attempts to synthesis bromine or chlorine heptafluoride have failed; instead, bromine or chlorine pentafluoride, as well as fluorine gas, are created.

Preparation of Interhalogen compounds

Under some conditions, these molecules are generated by the direct combination of the action of a group 17 element with a lower interhalogen compound. For instance, at 437K, chlorine combines with an equal volume of fluorine to generate ClF. In the synthesis of group 17 fluorides, this approach is commonly employed.

Cl2 +F2  → 2ClF (473K)

I2 + Cl2  →2ICl

Uses of Interhalogen compounds

  1. These are solvents that are not aqueous in nature.
  2. In a few reactions, they act as a catalyst.
  3. These are fluorinating chemicals.

Sample Problems

Question 1: Why are interhalogen compounds covalent?


Because of the low electronegativity difference between halogens, interhalogen compounds are covalent.

Question 2: What is the difference in the electronegativities of interhalogen compounds? 


The polarisation of the link is caused by the variation in electronegativities of interhalogen chemicals. Interhalogen compounds are thus more reactive than halogens due to their polarity and poor bonding.

Question 3: Why Are Interhalogen Compounds More Reactive than Halogens? 


Except for fluorine, interhalogen compounds are more reactive than all other halogens. Interhalogen compounds are more reactive than all other halogens because they all hydrolyze and ionise to form polyatomic ions. Because overlapping between orbitals of different atoms is less effective, interhalogen compounds have lower bond energies than halogens.

Question 4: What are Interhalogen Compounds? 


Halogen subordinates are interhalogen compounds. Interhalogen compounds are those that include two separate types of halogens.

Question 5: Can Fluorine Ever Be a Central Atom?


In interhalogen compounds, fluorine cannot be a core particle. This is due to the fact that it is part of the periodic table’s second cycle. It can only make one bond because it contains seven valence electrons.

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