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Group 17 Elements: Halogen Family | Inorganic Chemistry PDF Download


Physical Properties of the Halogens 

S. No.PropertiesFClBrI
1.Atomic Number91735153
2.Electronic configuration(He)2s22p5+(Ne)3s23p5[Ar] 3d104s2
[Kr] 4d105s2
3.Atomic radius/pm7299114133
4.(IE)I/kJ mol–11681125611431009
5.Electronegativity (Pauling)
6.Bond energy (XX)kJ mol–1126210158118
7.Oxidising power (X2)Most--Least
8.Common oxidation state-1

–1, +1, +3, 

+5, +7

–1, +1, +3, –

1, +5, +1, +3, 


+5, +1
9.Physical form (X2) at room temperature paleYellow gasYellow-green gasDark red liquidViolet-black solid
10.Melting point (X2)/°C–219–101–7114
  • HF has a high b.p. (19.5 °C) as a result of strong intermolecular hydrogen bonding, whereas all other hydrogen halide have much lower b.p.
  • HF is a weak acid, whereas all other hydrohalic acids (HCl, HBr and HI) are strong acids. 
  • F2 reacts with cold NaOH solution to produce OF2 (oxygen diflu oride) gas 2F2 + 2NaOH → 2NaF + H2O + OF2 The same reaction with chlorine or bromine produces a halides (X) and hypohalite (XO) X2 + 2NaOH → NaX + NaXO + H2O X stands for Cl or Br, Iodine (I2) does not react under the same condition 
  • Ca(OH)2 + Cl2 →CaCl(OCl) + H2
  • Hot NaOH 6NaOH + 3X2→ 5NaX + NaXO3 + 3H2O (X = Cl, Br, I)

Reactions of Halogen


2F2 + 2H2O →4H+ + 4F + O2

2X2 + 2H2O → 4H+ + 4X + O2

X2 + H2O Group 17 Elements: Halogen Family | Inorganic Chemistry  X + HOX + H+

Vigorous reaction with F2 Atmospheric O2 can oxidize I– to I2 hence, reverse rea ction Cl2 > Br2 > I2 (F2 does not disproportionate) All the halogens with Br2 photo chemical reaction, with I2 very slow even at high temperature.
H2 + X2 → 2MXn
Most metals form halides.
CO + X2 → COX2
Only Cl2, Brform carbonyl halide

2P + 3X→ 2PX3

2P + 5X2 → 2PX5

For F, Cl, Br, I For F, Cl, Br


2S + X2 → S2X2

S + 2Cl2 → SCl4

S + 3F2 → SF6

Cl, Br
H2S + X2 → 2HX + S
All the halogens oxidize H2S(S2–) to S
SO2 + X2 → SO2X2
F and Cl
8NH3 + 3X2 → N2 + 6NH4X
F, Cl, Br
X2 + X’2 → 2XX’

Interhalogen compound 

Compounds of Halogens With Oxygen

1. Oxides of fluorine 

(a) IF2
2F2 + 2NaOH →2NaF + H2O + OF2
Group 17 Elements: Halogen Family | Inorganic ChemistryStrong fluorinating agene
(b) O2F2
F2 + O2Group 17 Elements: Halogen Family | Inorganic Chemistry O2F2Similar to H2O2
Strong fluorinating agene
2. Oxides of chlorine 

(a) Cl2O
2Cl2 + 2Na2CO3 + H2O→Cl2O + 2NaHCO3 + 2NaCl
Group 17 Elements: Halogen Family | Inorganic ChemistryExplosive in nature
(b) ClO2
2AgClO+ Cl2 → 2AgCl + 2ClO2 + O2 2KClO3 + 2(COOH)2 → 2ClO2 + 2CO2 + (COOK)2 + 2H2O
Group 17 Elements: Halogen Family | Inorganic ChemistryOdd electron molecule but do not dimerise because odd electron is delocalize
(c) Cl2O6
2ClO2 + 2O3 → 2ClO3 + 2O2 → Cl2O+ 2O2
Group 17 Elements: Halogen Family | Inorganic ChemistryDiamagnetic in nature

Pseudohalogens and Pseudohalides 

A few ions are known consisting of two or more atoms of which at least one is N that have properties similar to those of the halide ions. They are therefore called pseudohalide ions. Pseudohalide ions are univalent and these form salts resembling the halide salts. For example the sodium salts are soluble in water, but the silver salts are insoluble. The hydrogen compounds are acids like the halogen acids HX.

Table: The important pseudohalogens

CN cyanide ion SCN thiocyanate ion SeCN selenocyanate ion OCN cyanate ion NCN2– cyanamide ion ONC– fulminate ion N3 azide ion
HCN hydrogen cyanide HSCN thiocyanic acid HOCN cyanic acid H2NCN cyanamide HONC fulminic acid HN3 hydrogen azide
(CN)2 cyanogen (SCN)2 thiocyanogen (SeCN)2 selenocyanogen

Some of the pseudohalide ions combine to form dimers comparable with the halogen molecules X2. These include cyanogens (CN)2, thiocyanogen (SCN)2 and selenocyanogen (SeCN)2. The best known pseudohalide is CN. This resembles Cl, Br and I in the following respects. 

1. It forms an acid HCN 

2. It can be oxidized to form a molecule cyanogens (CN)2

3. It forms insoluble salts with Ag+, Pb2+ and Hg+ 

4. Interpseudohalogen compounds ClCN, BrCN and ICN can be formed. 

5. AgCN is insoluble in water but solube in ammonia, as is AgCl. 

6. It forms a large number of complexes similar to halide complexes. e.g. [Cu(CN)4]2– and [CuCl4]2– and [Co(CN)6]3– and [CoCl6]3–




1Atomic Number
2Atomic mass

3Electronic configuration
[He] 2s22p6
[Ne] 3s22p6

[Ar] 3d104s24p6
[Kr] 4d105s25p6
4Atomic Radius (pm)
5Ioniza tion enthalpy (kJ mol–1)


6Boiling point /K


Initially their electronegativities were taken to be zero. But it is not zero.

 1. All are gases at room temperature. The only radioactive element in them is Radon (Rn) 2. Order of abundance in the air Ar > Ne > Kr > He > Xe 3. If Helium is compressed and liquefied it forms He(l) liquid at 4.2 K. This liquid is a normal liquid like any other liquid. But if it is further cooled then He(II) is obtained at 2.2 K. Which is known as super fluid because it is a liquid with properties of gases. It climbs through the walls of the container & comes out. It has very high thermal conductivity & very low viscosity. Compounds of inert gases are of following two types:

(i) Clatherate Compounds

Intert gas molecules get trapped in the cages formed by the crystal structure water.

During the formation of ice Xe atoms will be trapped in the cavities (or cages) formed by the water molecules in the crystal structure of ice. Compound thus obtained are called clatherate compounds. There are no chemical bonds in clatherate compound.

Group 17 Elements: Halogen Family | Inorganic Chemistry

Uses of Noble, Gases 

1. Uses of Helium 

(i) The chief use of helium is in filling of balloons which are employed for meterologica l observations. Althoughs lifting power of helium is 8% less then that of hydrogen, yet it is preferred because it is non-inflammable.

(ii) Liquid helium (b.p. 4.2 K) is used a s a cryogenic agent for carrying out various experiments at low temperatures.

(iii) An oxygen-helium mixture is used for artificial respiration in deep sea cliving. 

(iv) Helium is less soluble in blood than nitrogen. Therefore, an oxygen helium mixture is also used in die treatment of asthma.

(v) Helium is also used for creating inert atmosphere during welding of Mg and Al which are easily oxidizable.

(vi) Helium is chemically inactive and does not become radioactive. Hence it is used in gas cooled atomic reactors as a heat transfer agent.

2. Uses of Neon

(i) Neon is mainly used in discharge tubes and fluorescent lamps for advertising purpose. (ii) Neon has a remarkable property of carrying extremely high currents even under high voltage. Therefore, neon is used in safety devices for protecting electrical instruments such as voltmeters, relays and rectifiers from high voltage. 

(iii) It is used in becon light a s safety signal for air nevigators since its light ha s fog penetration power. 

(iv) It is used for filling sodium vapour lamps.

3. Uses of Argon

(i) Argon is used mainly to provide an inert atmosphere in high temperature metallurgical processes such as are welding of metals and alloys. 

(ii) It is used in filling incandescent and flourore scent lamps where its presence retards the sublimation of the filament and thus increases the life of the lamp. 

(iii) It is also used in ‘neon signs’ for obtaining lights of different colours.

4. Uses of Krypton

(i) Krypton and xenon are more efficient than argon in gas filled lamps because of their lower thermal conductivities but due to their scarcity and high cost they are used to a much smaller extent. 

(ii) A mixture of krypton and xenon has also been used in some tubes for high speed photography.

5. Uses of Radon

(i) Being radioactive, radon is used in radioactive research. 

(ii) It is used for normal treatment of cancer and other malignant research. 

(iii) It is used in X-ray photography for the detection of flaws in metals and other solids.


(a) Xenon difluoride (XeF2)

(i) Group 17 Elements: Halogen Family | Inorganic Chemistry

2. Xe + O2F2 Group 17 Elements: Halogen Family | Inorganic Chemistry XeF2 + O2


1. XeF2 + H2 → Xe + 2HF 

2. 2XeF+ 2H2O → 2Xe + 4HF + O2 (Slow) 

3. XeF2 + 2NaOH → Xe + 1/2 O2 + 2NaF + H2O (fast)

Oxidizing Properties

The standard reduction potential for XeF2 is measured to be +2.64 V. Therefore it acts as a strong oxidizing agent.

1. 2e + 2H+ + XeF2 → Xe + 2HF (SRP = + 2.64 V) 

2. XeF2 + 2NaX → Xe + X2 + 2NaF 

In this manner XeF2 will oxidize halideions (except F– into free halogens) 

3. S+ 24 XeF2 → 8SF6 + 24 Xe 

4. 2CrF2 + XeF2 → 2CrF3 + Xe

5. Group 17 Elements: Halogen Family | Inorganic Chemistry

6. 8NH3 + 3XeF2 → N2 + 6NH4F + 3Xe 

7. 2NO2 XeF2 → 2NO2F (Nitronium fluoride) + Xe 

8. IF5 (lewis acid) + XeF2 → [XeF]+ [IF6]–; 2SbF5(Lewis acid) + XeF2 → [XeF] + [SbF6]

(b) Xenon Tetrafluoride (XeF4) 

Structure: Shape square planar & Geometry octahedral

Group 17 Elements: Halogen Family | Inorganic Chemistry


1. 6XeF4 + 12H2O → 4XeO3 + 24 HF + 3O2 + 4Xe It disproportionate into perxenate ion in basic medium.

 (i) [XeO]64–Group 17 Elements: Halogen Family | Inorganic ChemistryXeO3 + O2 

(ii) [XeO]64– + Mn+2 → MnO4– + XeO3 (slow decomposition) 

2. XeF4 + SbF5 →[XeF3]+ [SbF6]

3. Fluorinating agent

XeF4 + Pt → PIF4 + Xe; XeF4 + 4NO→ Xe + 4NOF (nitrosyl fluoride)

XeF4 + 4NO2 ¾¾® Xe + 4NO2 F (nitronium fluoride)

4. Xenon Hexafluoride (XeF6)

Group 17 Elements: Halogen Family | Inorganic Chemistry

Solid XeF6 exists as tetramer in which 2[XeF5]+ ions are by F ions

Group 17 Elements: Halogen Family | Inorganic Chemistry


(i) HF is a good solvent for all three flu orides. 

(ii) Hydrolysis 

(a) Complete hydrolysis: XeF6 + 3H2O → XeO3 (white solid) + 2HF 

(b) Partial hydrolysis:

Group 17 Elements: Halogen Family | Inorganic Chemistry

(iii) Reaction with silica (SiO2): 2XeF6 + SiO2 → 2XeOF4 + SiF4 

(iv) Thermal decomposition (effect of heat): 2 XeF6 Group 17 Elements: Halogen Family | Inorganic Chemistry XeF2 + XeF4 + 3FXeF2 and XeF4 do not undergo decomposition

(v) Formation of addition compounds XeF6 + SbF→ [XeF5]+ [SbF6]; XeF6 + BF3 → [XeF5]+ [BF4] 

(vi) Reaction with H2 

XeF6 + 3H2 → 6HF + Xe; 

(vii) XeO3 + 2XeF6 → 3XeOFOrder of oxidizing power XeF2 > XeF4 > XeF6 

(viii) F—donating/F-accepting properties Donating XeF+ PtF5 →(XeF5I) (PtF6–)

Group 17 Elements: Halogen Family | Inorganic Chemistry

The document Group 17 Elements: Halogen Family | Inorganic Chemistry is a part of the Chemistry Course Inorganic Chemistry.
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FAQs on Group 17 Elements: Halogen Family - Inorganic Chemistry

1. What are the elements in Group 17 known as?
Ans. The elements in Group 17 are known as the Halogen family. They include fluorine, chlorine, bromine, iodine, and astatine.
2. What are the properties of halogens?
Ans. Halogens have several distinct properties. They are highly reactive and tend to form compounds with other elements. They have a strong odor and are often toxic. They can exist in all three states of matter at room temperature, with fluorine and chlorine being gases, bromine a liquid, and iodine a solid.
3. What are some common uses of halogens?
Ans. Halogens have various uses in different industries. Chlorine is commonly used as a disinfectant in water treatment and as a bleach. Iodine is used as an antiseptic and in the production of pharmaceuticals. Fluorine is used in the production of toothpaste and non-stick coatings. Bromine is used in flame retardants and in the production of dyes.
4. Why are halogens highly reactive?
Ans. Halogens are highly reactive because they have seven valence electrons in their outermost energy level. They require only one additional electron to achieve a stable electron configuration, leading to a strong tendency to gain or share electrons with other elements. This reactivity is why halogens readily form compounds with other elements.
5. What is the trend in reactivity within the halogen family?
Ans. The reactivity of halogens decreases as you move down the group. This is because the atomic size increases, and the outermost electrons are farther from the nucleus. As a result, it becomes harder for the halogens to attract an additional electron, making them less reactive. Fluorine is the most reactive halogen, while astatine is the least reactive.
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