Other Compounds of the Halogen Family

The halogen family, also known as Group 17 of the periodic table, consists of the elements fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). These elements are known for their high reactivity, particularly fluorine, which is the most reactive of all. Halogens form a variety of compounds, both with other halogens and with elements from other groups. In this article, we will explore some of the other compounds of the halogen family, beyond the simple diatomic molecules (e.g., F2, Cl2, Br2, I2).

Interhalogen Compounds

Interhalogen compounds are formed by the combination of two different halogens. They have the general formula XYn, where X and Y are different halogens and n can be 1, 3, 5, or 7.

Properties and Examples

Compound	Structure	Physical State	Color
ClF	Linear	Gas	Colorless
BrF3	T-shaped	Liquid	Pale yellow
ICl	Linear	Solid	Yellow-brown
IF5	Square pyramidal	Liquid	Pale yellow
ClF3	T-shaped	Liquid	Green-yellow

Preparation

Interhalogen compounds are typically prepared by direct combination of the halogens under specific conditions. For example:

$$ \text{Cl}_2(g) + 3\text{F}_2(g) \rightarrow 2\text{ClF}_3(l) $$

Reactivity

Interhalogen compounds are generally more reactive than the diatomic halogen molecules from which they are formed. They are powerful oxidizing agents and can react with a wide range of substances.

Halogen Oxides

Halogen oxides are compounds formed between halogens and oxygen. They are less stable than interhalogen compounds and can be quite reactive.

Properties and Examples

Compound	Structure	Physical State	Color
Cl2O	Bent	Gas	Yellow-green
ClO2	Bent	Gas	Yellow
Br2O	Bent	Gas	Orange
I2O5	-	Solid	White

Preparation

Halogen oxides can be prepared by the reaction of halogens with oxygen or by the decomposition of certain halogen-containing compounds. For example:

$$ 2\text{Cl}_2(g) + 2\text{O}_2(g) \rightarrow 2\text{Cl}_2\text{O}(g) $$

Reactivity

Halogen oxides are strong oxidizing agents and can react with many organic and inorganic substances. They are often unstable and can decompose explosively.

Halogen Oxyacids

Halogen oxyacids are compounds that contain halogens, oxygen, and hydrogen. They are formed when halogen oxides react with water.

Properties and Examples

Acid	Formula	Oxidation State of Halogen	Strength
Hypochlorous	HClO	+1	Weak
Chlorous	HClO2	+3	Weak
Chloric	HClO3	+5	Strong
Perchloric	HClO4	+7	Very strong

Preparation

Hypochlorous acid can be prepared by dissolving chlorine gas in water:

$$ \text{Cl}_2(g) + \text{H}_2\text{O}(l) \rightarrow \text{HClO}(aq) + \text{HCl}(aq) $$

Other oxyacids can be prepared by the oxidation of lower oxyacids or their salts.

Reactivity

The strength of halogen oxyacids increases with the oxidation state of the halogen. Perchloric acid, for example, is one of the strongest acids known.

Polyhalides

Polyhalides are compounds that contain more than one type of halogen ion. They are formed when halogen ions combine with interhalogen compounds.

Properties and Examples

Compound	Composition	Physical State
ICl2^-	I^- + ICl	Solid
IBr2^-	I^- + IBr	Solid
IF6^-	I^- + IF5	Solid

Preparation

Polyhalides can be prepared by mixing halide salts with interhalogen compounds in the appropriate stoichiometric ratios.

Reactivity

Polyhalides are generally less reactive than the interhalogen compounds from which they are formed. They can be used as sources of halide ions in various chemical reactions.

Summary

The halogen family forms a wide variety of compounds, including interhalogen compounds, halogen oxides, halogen oxyacids, and polyhalides. These compounds exhibit a range of properties and reactivities, making them important in both industrial applications and laboratory chemistry. Understanding the chemistry of these compounds is essential for students preparing for exams in inorganic chemistry.