Chapter 6th:- Preparation Properties & Structures of BorazineDiboraneHydrazineInterhalogens, Polyhalides, and Fluorides of Xenon 1st year Book
(Page 7)

Structure of AB3 type of Interhalogen molecules 

The Lewis structure of the AB3 molecule is :

It is clear from the above structure that:
Number of bonding electrons pairs (bp ‘s) =3
Number of non-bonding electrons pairs (lp ‘s) =2
Ab3 interhalogen molecules formate
sp3 hybridization image, first excitation state
Where, A = Cl, Br or I and n = 3 (for Cl), 4 (for Br) or 5(for I)

Overlapping of orbitals in AB2 molecule:

sp3d-p overlapping
fig: (a) sp3d-p overlapping between A and B atom structure (b) structure of AB3 molecules
  1. ClF3 molecule: in this molecule chlorine is the central atom which undergoes sp3d hybridization as shown below:

chlorine sp3d hybridization

From the above hybridization scheme, it is evident that the central atom, Cl consists of two filled sp3d hybrid orbitals ( (p′s) and three half-filled sp3d hybrid orbitals which overlap with singly filled 2pz orbital of F-atom to give the following structure.

2. BrFBr3 has the same hybridization and structure as ClF3.
Fig: 6.07: (a) Head-to-head overlapping of half-hilled sp3d hybrid orbitals of Br-atom with a half-filled 2pz-atomic orbital of F-atoms and the formation of sp3 d−p; o-bonds (b) BrF3 molecule with T-shape
3. ICl3 molecule: X-ray analysis of the crystal of ICl3 established the dimeric form of the molecule which has the following bridged structure :

Figure 8.08: Structure of (Cl3)2
The dimer (CCl3)2 is formed by joining two T-shaped CC3 molecules. In dimeric form, each Iodine atom exhibits sp3 d hybridization as exhibited by Cl in the ClF3 molecule (or in the general description mentioned above), The (ICl3) molecule does not have the expected regular trigonal pyramidal shape but has a square planar shape. In which
Uses: It is used in medicines and in the preparation of poly-halides.

 Compounds of the AX3 type:

Chlorine trifluoride, ClF3


lt ray be prepared by treating chlorine or chlorine monofluoride with an excess of chlorine.


(i) It is a colorless liquid that gives dense white fumes to air and decomposes in the presence of moist air. Its freezing point is −82.6∘C and its boiling point is 12.1∘C.
(iii) It reacts with almost all elements except for inert gases, nitrogen, and a few passive metals.
(iii) it is an extremely reactive and powerful fluorinating agent. It reacts with AgF and CoF2 to form AgF2and CoF3respectively.
(iv) It destroys glass, and quartz and inflames organic substances.
(v) It reacts with water to give a red liquid which crystallizes at −70∘C and is found to be CIFO.


(i) it is used in incendiary and in cutting off well tubes.
(ii) it is used for fluorination of various compounds.
(iii) it is recommended as an oxidizer for propellants.

Chlorine trifluoride, BrF3

Preparation :

It may be prepared by the following methods:
(i) On mixing fluorine with bromine in nitrogen.
(ii) By the action of F2 on metal bromide
(iii) By the action of Br2 on CFF3 at 10.∘C
(iv) By the action of F2 on HBr
2HBr+3 F2⟶2BrF3+H2
(v) By the disproportionation of BrF

Properties :

(i) It is a colourless yellow fuming liquid.
(ii) Its melting point and boiling points are 90∘Cand 127∘Crespectively.
(iii) It is violently decomposed by water and organic materials. It has electrical high conductivity and ionizes as:
2BrF3 ⟶BrF2+BrF4−
(iv) it reacts with glass and silica materials and sets fire to the wood, paper, etc. It displaces O2 gas from oxides.
(v) It gives an additional reaction withK2[PdCl6].

Uses :

(i) it is used as a fluorinating agent.
(ii) H is used to prepare polyhalides.

Iodine trichloride, ICl3


It is best prepared as follows :
(i) By condensing excess of Cl2 on I2 at −80∘C or by passing Cl2 over I2 until this is converted into ICl and then raising the temperature at 100∘C.
(ii) By the reaction of iodine pentoxide and hydrogen chloride.
(iii) By the reaction of potassium iodide and potassium iodate with hydrochloric acid.
(iv) By the reaction of HI on Cl2.

Properties :

(i) It is a deliquescent needies like solid, lemon yellow in colour (m.p. 101 degrees C) with a pungent smell.
(ii) It is unstable and decomposes as :
(iii) It is soluble in organic solvents, liquid SO2 and liquid NH3.
(iv) it gets hydrolyzed by water.
(v) On electrolysis, chlorine is set free at the anode and iodine at the cathode.
(vi) It gives additive compounds with some metallic fluorides such as KF, AbF, etc.
KF + ICl ⟶ KICl3F
RbF + ICl3 ⟶ RbICl3F
(vii) It reacts with carbon disulfide.
(viii) it is easily decomposed by alkali hydroxide solution.


Related Part: Compounds of the AX type,   Compounds of the AX3 type


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