Interhalogen
Encyclopedia
The halogens react with each other to form interhalogen compounds.
The general formula of most interhalogen compounds is XYn, where n = 1, 3, 5 or 7, and X is the less electronegative
of the two halogens. They are all prone to hydrolysis
, and ionise
to give rise to polyatomic ion
s.
character, the less electronegative element
, X, being oxidised and having a partial positive charge. Most combinations of F, Cl, Br and I are known, but not all are stable.
Chlorine monofluoride
(ClF)
The lightest interhalogen compound, ClF is a colorless gas with a normal boiling point of −100 °C.
Bromine monofluoride (BrF)
BrF has not been obtained pure — it dissociates into the trifluoride and free bromine
.
Iodine monofluoride
(IF)
IF is unstable and decomposes at 0 C, disproportionating into elemental iodine and iodine pentafluoride
.
Bromine monochloride
(BrCl)
A red-brown gas with a boiling point of 5 °C.
Iodine monochloride
(ICl)
Red transparent crystals which melt at 27.2° C to form a choking brownish liquid (similar in appearance and weight to bromine
). It reacts with HCl to form the strong acid HICl2. The crystal structure
of iodine monochloride consists of puckered zig-zag chains, with strong interactions between the chains.
Iodine monobromide
(IBr)
Made by direct combination of the elements to form a dark red crystalline solid. It melts at 42° C and boils at 116° C to form a partially dissociated vapour.
The general formula of most interhalogen compounds is XYn, where n = 1, 3, 5 or 7, and X is the less electronegative
Electronegativity
Electronegativity, symbol χ , is a chemical property that describes the tendency of an atom or a functional group to attract electrons towards itself. An atom's electronegativity is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus...
of the two halogens. They are all prone to hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
, and ionise
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
to give rise to polyatomic ion
Polyatomic ion
A polyatomic ion, also known as a molecular ion, is a charged species composed of two or more atoms covalently bonded or of a metal complex that can be considered as acting as a single unit in the context of acid and base chemistry or in the formation of salts. The prefix "poly-" means "many," in...
s.
Diatomic interhalogens
The interhalogens of form XY have physical properties intermediate between those of the two parent halogens. The covalent bond between the two atoms has some ionicIonic bond
An ionic bond is a type of chemical bond formed through an electrostatic attraction between two oppositely charged ions. Ionic bonds are formed between a cation, which is usually a metal, and an anion, which is usually a nonmetal. Pure ionic bonding cannot exist: all ionic compounds have some...
character, the less electronegative element
Chemical element
A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. Familiar examples of elements include carbon, oxygen, aluminum, iron, copper, gold, mercury, and lead.As of November 2011, 118 elements...
, X, being oxidised and having a partial positive charge. Most combinations of F, Cl, Br and I are known, but not all are stable.
Chlorine monofluoride
Chlorine monofluoride
Chlorine monofluoride is a volatile interhalogen compound with the chemical formula ClF. It is a colourless gas at room temperature and is stable even at high temperatures. When cooled to −100 °C, ClF condenses as a pale yellow liquid...
(ClF)
The lightest interhalogen compound, ClF is a colorless gas with a normal boiling point of −100 °C.
Bromine monofluoride (BrF)
BrF has not been obtained pure — it dissociates into the trifluoride and free bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
.
Iodine monofluoride
Iodine monofluoride
Iodine monofluoride is an interhalogen compound of iodine and fluorine with formula IF. It is a chocolate-brown solid that decomposes at 0 C, disproportionating to elemental iodine and iodine pentafluoride:...
(IF)
IF is unstable and decomposes at 0 C, disproportionating into elemental iodine and iodine pentafluoride
Iodine pentafluoride
Iodine pentafluoride is an interhalogen compound with chemical formula IF5. It is a fluoride of iodine. It is a colourless or yellow liquid with a density of 3.250 g cm−3. It was first synthesized by Henri Moissan in 1891 by burning solid iodine in fluorine gas...
.
Bromine monochloride
Bromine monochloride
Bromine monochloride, also called bromine chloride, bromochloride, and bromine chloride, is an interhalogen inorganic compound with chemical formula BrCl. It is an unstable brownish yellow gas with boiling point 5°C and melting point −66 °C. Its CAS number is 13863-41-7 and its EINECS number is...
(BrCl)
A red-brown gas with a boiling point of 5 °C.
Iodine monochloride
Iodine monochloride
Iodine monochloride is an interhalogen compound with the formula ICl. It is a red-brown compound that melts near room temperature. Because of the difference in the electronegativity of iodine and chlorine, ICl is highly polar and behaves as a source of I+....
(ICl)
Red transparent crystals which melt at 27.2° C to form a choking brownish liquid (similar in appearance and weight to bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
). It reacts with HCl to form the strong acid HICl2. The crystal structure
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
of iodine monochloride consists of puckered zig-zag chains, with strong interactions between the chains.
Iodine monobromide
Iodine monobromide
Iodine monobromide is a dark red interhalogen compound that forms when iodine and bromine are combined.-Synthesis:Iodine monobromide is produced by the simple combination of iodine and bromine in a 1:1 molar ratio, according to the equation...
(IBr)
Made by direct combination of the elements to form a dark red crystalline solid. It melts at 42° C and boils at 116° C to form a partially dissociated vapour.
Tetra-atomic interhalogens
- Chlorine trifluorideChlorine trifluorideChlorine trifluoride is an interhalogen compound with the formula ClF3. This colourless, poisonous, corrosive and very reactive gas condenses to a pale-greenish yellow liquid, the form in which it is most often sold...
(ClF3) is a colourless gas which condenses to a green liquid, and freezes to a white solid. It is made by reacting chlorine with an excess of fluorine at 250° C in a nickelNickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
tube. It reacts more violently than fluorine, often explosively. The molecule is planar and T-shaped. It is used in the manufacture of uranium hexafluorideUranium hexafluorideUranium hexafluoride , referred to as "hex" in the nuclear industry, is a compound used in the uranium enrichment process that produces fuel for nuclear reactors and nuclear weapons. It forms solid grey crystals at standard temperature and pressure , is highly toxic, reacts violently with water...
. - Bromine trifluorideBromine trifluorideBromine trifluoride is an interhalogen compound with the formula BrF3. This toxic, colourless, and corrosive liquid is soluble in sulfuric acid but explodes on contact with water and organic compounds. It is a powerful fluorinating agent and an ionizing inorganic solvent...
(BrF3) is a yellow green liquid which conducts electricity — it ionises to form [BrF2+] + [BrF4−]. It reacts with many metals and metal oxides to form similar ionised entities; with some others it forms the metal fluoride plus free bromine and oxygenOxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
. It is used in organic chemistryOrganic chemistryOrganic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
as a fluorinating agent. It has the same molecular shape as chlorine trifluoride. - Iodine trifluorideIodine trifluorideIodine trifluoride is an interhalogen compound with the chemical formule IF3. It is a yellow solid which decomposes above −28 °C. It can be synthesised from the elements, but care must be taken to avoid the formation of IF5.-Reactions:...
(IF3) is a yellow solid which decomposes above −28 °C. It can be synthesised from the elements, but care must be taken to avoid the formation of IF5Iodine pentafluorideIodine pentafluoride is an interhalogen compound with chemical formula IF5. It is a fluoride of iodine. It is a colourless or yellow liquid with a density of 3.250 g cm−3. It was first synthesized by Henri Moissan in 1891 by burning solid iodine in fluorine gas...
. F2FluorineFluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
attacks I2IodineIodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
to yield IF3 at −45 °C in CCl3FTrichlorofluoromethaneTrichlorofluoromethane, also called freon-11, CFC-11, or R-11, is a chlorofluorocarbon. It is a colorless, nearly odorless liquid that boils at about room temperature.- Uses :It was the first widely used refrigerant...
. Alternatively, at low temperatures, the fluorination reaction I2 + 3XeF2Xenon difluorideXenon difluoride is a powerful fluorinating agent with the chemical formula , and one of the most stable xenon compounds. Like most covalent inorganic fluorides it is moisture sensitive. It decomposes on contact with light or water vapour. Xenon difluoride is a dense, white crystalline solid. It...
→ 2IF3 + 3XeXenonXenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
can be used. Not much is known about iodine trifluoride as it is so unstable. - Iodine trichlorideIodine trichlorideIodine trichloride is an interhalogen compound of iodine and chlorine. It is bright yellow and in the solid state is present as a planar dimer I2Cl6, Cl2I2ICl2, with two bridging Cl atoms....
(ICl3) forms lemon yellow crystals which can be melted under pressure to a brown liquid. It can be made from the elements at low temperature, or from iodine pentoxide and hydrogen chloride. It reacts with many metal chlorides to form tetrachloriodides, and hydrolyses in water. The molecule is a planar dimer, with each iodine atom surrounded by four chlorine atoms.
Hexa-atomic interhalogens
- Chlorine pentafluorideChlorine pentafluorideChlorine pentafluoride is an interhalogen compound with formula ClF5. It was first synthesized in 1963.Its square pyramidal structure with C4v symmetry was confirmed by its high resolution19F NMR spectrum.-Preparation:...
(ClF5) is a colourless gas, made by reacting chlorine trifluoride with fluorine at high temperatures and high pressures. It reacts violently with water and most metals and nonmetalNonmetalNonmetal, or non-metal, is a term used in chemistry when classifying the chemical elements. On the basis of their general physical and chemical properties, every element in the periodic table can be termed either a metal or a nonmetal...
s. - Bromine pentafluorideBromine pentafluorideBromine pentafluoride, BrF5, is an interhalogen compound and a fluoride of bromine. It is a strong fluorination reagent.It melts at −61.30 °C and boils at 40.25 °C. BrF5 finds use in oxygen isotope analysis. Laser ablation of solid silicates in the presence of bromine pentafluoride releases O2 for...
(BrF5) is a colourless fuming liquid, made by reacting bromine trifluoride with fluorine at 200° C. It is physically stable, but reacts violently with water and most metals and nonmetalNonmetalNonmetal, or non-metal, is a term used in chemistry when classifying the chemical elements. On the basis of their general physical and chemical properties, every element in the periodic table can be termed either a metal or a nonmetal...
s. - Iodine pentafluorideIodine pentafluorideIodine pentafluoride is an interhalogen compound with chemical formula IF5. It is a fluoride of iodine. It is a colourless or yellow liquid with a density of 3.250 g cm−3. It was first synthesized by Henri Moissan in 1891 by burning solid iodine in fluorine gas...
(IF5) is a colourless liquid, made by reacting iodine pentoxide with fluorine, or iodine with silver fluoride. It is highly reactive, even slowly with glass. It reacts with elements, oxides and carbon halides. The molecule has the form of a tetragonal pyramid.
Octa-atomic interhalogens
- Iodine heptafluorideIodine heptafluorideIodine heptafluoride, also known as iodine fluoride or even iodine fluoride, is an interhalogen compound with chemical formula IF7. It has an unusual pentagonal bipyramidal structure, as predicted by VSEPR theory...
(IF7) is a colourless gas. It is made by reacting the pentafluoride with fluorine. IF7 is chemically inert, having no lone pair of electrons in the valency shell; in this it resembles sulfur hexafluorideSulfur hexafluorideSulfur hexafluoride is an inorganic, colorless, odorless, and non-flammable greenhouse gas. has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom. It is a hypervalent molecule. Typical for a nonpolar gas, it is poorly soluble in water but soluble in...
. The molecule is a pentagonal bipyramid. This compound is the only interhalogen compound possible where the larger atom is carrying seven of the smaller atoms.
- All attempts to form bromine heptafluoride have met with failure; instead, bromine pentafluoride and fluorine gas are produced.
Summary of known interhalogens
| F | Cl | Br | I | |
| F | Fluorine Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic... |
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| Cl | Chlorine monofluoride Chlorine monofluoride is a volatile interhalogen compound with the chemical formula ClF. It is a colourless gas at room temperature and is stable even at high temperatures. When cooled to −100 °C, ClF condenses as a pale yellow liquid... , ClF3 Chlorine trifluoride Chlorine trifluoride is an interhalogen compound with the formula ClF3. This colourless, poisonous, corrosive and very reactive gas condenses to a pale-greenish yellow liquid, the form in which it is most often sold... , ClF5 Chlorine pentafluoride Chlorine pentafluoride is an interhalogen compound with formula ClF5. It was first synthesized in 1963.Its square pyramidal structure with C4v symmetry was confirmed by its high resolution19F NMR spectrum.-Preparation:... |
Chlorine Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine... |
||
| Br | Bromine trifluoride Bromine trifluoride is an interhalogen compound with the formula BrF3. This toxic, colourless, and corrosive liquid is soluble in sulfuric acid but explodes on contact with water and organic compounds. It is a powerful fluorinating agent and an ionizing inorganic solvent... , BrF5 Bromine pentafluoride Bromine pentafluoride, BrF5, is an interhalogen compound and a fluoride of bromine. It is a strong fluorination reagent.It melts at −61.30 °C and boils at 40.25 °C. BrF5 finds use in oxygen isotope analysis. Laser ablation of solid silicates in the presence of bromine pentafluoride releases O2 for... |
Bromine monochloride Bromine monochloride, also called bromine chloride, bromochloride, and bromine chloride, is an interhalogen inorganic compound with chemical formula BrCl. It is an unstable brownish yellow gas with boiling point 5°C and melting point −66 °C. Its CAS number is 13863-41-7 and its EINECS number is... |
Bromine Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826... |
|
| I | Iodine monofluoride Iodine monofluoride is an interhalogen compound of iodine and fluorine with formula IF. It is a chocolate-brown solid that decomposes at 0 C, disproportionating to elemental iodine and iodine pentafluoride:... , IF3 Iodine trifluoride Iodine trifluoride is an interhalogen compound with the chemical formule IF3. It is a yellow solid which decomposes above −28 °C. It can be synthesised from the elements, but care must be taken to avoid the formation of IF5.-Reactions:... , IF5 Iodine pentafluoride Iodine pentafluoride is an interhalogen compound with chemical formula IF5. It is a fluoride of iodine. It is a colourless or yellow liquid with a density of 3.250 g cm−3. It was first synthesized by Henri Moissan in 1891 by burning solid iodine in fluorine gas... , IF7 Iodine heptafluoride Iodine heptafluoride, also known as iodine fluoride or even iodine fluoride, is an interhalogen compound with chemical formula IF7. It has an unusual pentagonal bipyramidal structure, as predicted by VSEPR theory... |
Iodine monochloride Iodine monochloride is an interhalogen compound with the formula ICl. It is a red-brown compound that melts near room temperature. Because of the difference in the electronegativity of iodine and chlorine, ICl is highly polar and behaves as a source of I+.... , I2Cl6 Iodine trichloride Iodine trichloride is an interhalogen compound of iodine and chlorine. It is bright yellow and in the solid state is present as a planar dimer I2Cl6, Cl2I2ICl2, with two bridging Cl atoms.... |
Iodine monobromide Iodine monobromide is a dark red interhalogen compound that forms when iodine and bromine are combined.-Synthesis:Iodine monobromide is produced by the simple combination of iodine and bromine in a 1:1 molar ratio, according to the equation... |
Iodine Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor.... |