ElementsHydrogen Halides and also Halogen OxoacidsStates of matter at Room Temperature

The halogens are located on the left the the noble gases on the regular table. These 5 toxic, non-metallic facets make up group 17 the the regular table and consist of: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and also astatine (At). Return astatine is radioactive and also only has short-lived isotopes, it behaves similar to iodine and is often contained in the halogen group. Because the halogen aspects have seven valence electrons, they just require one extr electron to type a full octet. This characteristic renders them more reactive than various other non-metal groups.

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Halogens form diatomic molecule (of the kind X2​, whereby X denotes a halogen atom) in your elemental states. The bond in these diatomic molecules are non-polar covalent single bonds. However, halogens readily incorporate with most elements and are never ever seen uncombined in nature. Together a basic rule, fluorine is the most reactive halogen and also astatine is the the very least reactive. Every halogens kind Group 1 salt with similar properties. In this compounds, halogens are current as halide anions v charge that -1 (e.g. Cl-, Br-, etc.). Replacing the -ine ending with an -ide finishing indicates the visibility of halide anions; for example, Cl- is named "chloride." In addition, halogens act as oxidizing agents—they exhibition the building to oxidation metals. Therefore, most of the bsci-ch.orgical reactions the involve halogens space oxidation-reduction reaction in aqueous solution. The halogens often form single bonds, as soon as in the -1 oxidation state, with carbon or nitrogen in necessary compounds. As soon as a halogen atom is substituted because that a covalently-bonded hydrogen atom in an essential compound, the prefix halo- have the right to be offered in a general sense, or the prefixes fluoro-, chloro-, bromo-, or iodo- have the right to be used for particular halogen substitutions. Halogen elements can cross-link to kind diatomic molecules with polar covalent solitary bonds.

Chlorine (Cl2) was the very first halogen to be discovered in 1774, complied with by iodine (I2), bromine (Br2), fluorine (F2), and also astatine (At, uncovered last in 1940). The name "halogen" is obtained from the Greek roots hal- ("salt") and -gen ("to form"). With each other these words combine to typical "salt former", express the truth that halogens type salts as soon as they react v metals. Halite is the mineral name for rock salt, a natural mineral consisting essentially of sodium chloride (NaCl). Lastly, the halogens are likewise relevant in day-to-day life, even if it is it be the fluoride the goes in toothpaste, the chlorine that disinfects drinking water, or the iodine that facilitates the production of thyroid hormone in one"s body.


Fluorine - Fluorine has actually an atomic variety of 9 and also is denoted through the prize F. Elemental fluorine was an initial discovered in 1886 by isolating it from hydrofluoric acid. Fluorine exists as a diatomic molecule in its free state (F2) and is the many abundant halogen found in the Earth"s crust. Fluorine is the many electronegative aspect in the regular table. It appears as a pale yellow gas in ~ room temperature. Fluorine additionally has a reasonably small atom radius. That is oxidation state is constantly -1 except in the elemental, diatomic state (in which its oxidation state is zero). Fluorine is very reactive and reacts straight with all facets except helium (He), neon (Ne) and argon (Ar). In H2O solution, hydrofluoric acid (HF) is a weak acid. Although fluorine is extremely electronegative, the electronegativity go not determine its acidity; HF is a weak acid because of the reality that the fluoride ion is an easy (pH>7). In addition, fluorine to produce very an effective oxidants. For example, fluorine deserve to react v the noble gas xenon and form the strong oxidizing certified dealer Xenon Difluoride (XeF2). There are numerous uses for fluorine, which will certainly be questioned in component VI of this article.

Chlorine - Chlorine has actually the atom number 17 and the bsci-ch.orgical symbol Cl. Chlorine was uncovered in 1774 by extract it native hydrochloric acid. In its element state, it forms the diatomic molecule Cl2. Chlorine exhibits lot of oxidation states, such as -1, +1, 3, 5, and also 7. In ~ room temperature it appears as a light eco-friendly gas. Due to the fact that the bond the forms in between the 2 chlorine atoms is weak, the Cl2 molecule is really reactive. Chlorine reacts with steels to develop salts referred to as chlorides. Chloride ions space the many abundant ions that dissolve in the ocean. Chlorine additionally has two isotopes: 35Cl and 37Cl. Salt chloride is the many prevalent link of the chlorides.

Bromine - Bromine has actually an atomic variety of 35 v a price of Br. The was an initial discovered in 1826. In its element form, the is the diatomic molecule Br2. At room temperature, bromine is a reddish- brown liquid. The oxidation claims vary from -1, +1, 3, 4 and 5. Bromine is much more reactive 보다 iodine, however not together reactive as chlorine. Also, bromine has actually two isotopes: 79Br and also 81Br. Bromine consists of bromide salts, which have been discovered in the sea. The world production that bromide has increased significantly over the years, due to its accessibility and much longer existence. Like all of the other halogens, bromine is an oxidizing agent, and also is really toxic.

Iodine - Iodine has the atom number 53 and symbol I. Iodine has actually oxidation says -1, +1, 5 and also 7. Iodine exists as a diatomic molecule, I2, in its element state. In ~ room temperature, it appears as a violet solid. Iodine has one secure isotope: 127I. That was very first discovered in 1811 with the use of seaweed and sulfuric acid. Currently, iodide ions can be isolated in seawater. Although iodine is not an extremely soluble in water, the solubility may boost if specific iodides are combined in the solution. Iodine has many important duties in life, including thyroid hormone production. This will certainly be disputed in component VI of the text.

Astatine - Astatine is a radioactive element with one atomic number of 85 and symbol At. Its feasible oxidation says include: -1, +1, 3, 5 and 7. It is the only halogen the is not a diatomic molecule and also it appears as a black, metallic solid in ~ room temperature. Astatine is a really rare element, so there is not that lot known about this element. In addition, astatine has actually a really short radiation half-life, no much longer than a pair of hours. It was discovered in 1940 by synthesis. Also, the is assumed that astatine is comparable to iodine. However, this two facets are suspect to differ by your metallic character.

Table 1.1: Electron construction of the halogens. HalogenElectronic Configuration
Fluorine 1s2 2s2 2p5
Chlorine 3s2 3p5
Bromine 3d10 4s2 4p5
Iodine 4d10 5s2 5p5
Astatine 4f14 5d10 6s2 6p5

Melting and Boiling points (increases down the group)

The melting and boiling points increase down the group because of the van der Waals forces. The size of the molecules increases down the group. This rise in size way an rise in the strength of the valve der Waals forces.

Halogen Melting point (˚C) Boiling allude (˚C) Fluorine -220 -188 Chlorine -101 -35 Bromine -7.2 58.8 Iodine 114 184 Astatine 302 337

Atomic Radius (increases down the group)

The size of the nucleus boosts down a group (F since the numbers of protons and also neutrons increase. In addition, much more energy levels are added with each period. This outcomes in a larger orbital, and also therefore a longer atomic radius.

Table 1.3: atomic Radii the Halogens HalogenCovalent Radius (pm)Ionic (X-) radius (pm)
Fluorine 71 133
Chlorine 99 181
Bromine 114 196
Iodine 133 220
Astatine 150

Ionization energy (decreases under the group)

If the external valence electrons space not close to the nucleus, that does not take as much power to remove them. Therefore, the energy required to pull turn off the outermost electron is no as high because that the aspects at the bottom of the group since there are much more energy levels. Also, the high ionization energy makes the element appear non-metallic. Iodine and astatine display screen metallic properties, for this reason ionization energy decreases down the group (At Table 1.4 Ionization power of Halogens Halogen First Ionization energy (kJ/mol) Fluorine 1681 Chlorine 1251 Bromine 1140 Iodine 1008 Astatine 890±40

Electronegativity (decreases under the group)

The variety of valence electrons in one atom rises down the group as result of the boost in power levels at progressively lower levels. The electrons room progressively additional from the nucleus; therefore, the nucleus and the electrons are not together attracted to each other. Rise in shielding is observed. Electronegativity as such decreases under the team (At Table 1.5: Electronegativity that Halogens Halogen Electronegativity Fluorine 4.0 Chlorine 3.0 Bromine 2.8 Iodine 2.5 Astatine 2.2

Electron Affinity (decreases under the group)

Since the atom size rises down the group, electron affinity typically decreases (At Cl). An electron will not be together attracted to the nucleus, leading to a short electron affinity. However, fluorine has a reduced electron affinity 보다 chlorine. This can be explained by the small size that fluorine, contrasted to chlorine.

Table 1.6: Electron Affinity that Halogens HalogenElectron Affinity (kJ/mol)
Fluorine -328.0
Chlorine -349.0
Bromine -324.6
Iodine -295.2
Astatine -270.1

Reactivity of elements (decreases down the group)

The reactivities that the halogens decrease down the team ( at Cl atomic radius increases in size with rise of digital energy levels. This lessens the attraction for valence electron of other atoms, decreasing reactivity. This decrease also occurs because electronegativity decreases under a group; therefore, over there is less electron "pulling." In addition, there is a to decrease in oxidizing capability down the group.

Hydrogen Halides

A halide is developed when a halogen reacts v another, less electronegative facet to type a binary compound. Hydrogen, for example, reacts with halogens to form halides that the type HX:

Hydrogen Fluoride: HF Hydrogen Chloride: HCl Hydrogen Bromide: HBr Hydrogen Iodide: HI

Hydrogen halides easily dissolve in water to type hydrohalic (hydrofluoric, hydrochloric, hydrobromic, hydroiodic) acids. The nature of these acids are provided below:

The mountain are developed by the adhering to reaction: HX (aq) + H2O (l) → X- (aq) + H3O+ (aq) every hydrogen halides type strong acids, other than HF The mountain of the hydrohalic acids increases as follows: HF

Hydrofluoric acid have the right to etch glass and certain inorganic fluorides over a long period of time.

It may seem counterintuitive come say the HF is the weakest hydrohalic acid because fluorine has actually the highest electronegativity. However,​ the H-F shortcut is very strong; if the H-X bond is strong, the resulting acid is weak. A strong bond is determined by a short bond length and also a large bond dissociation energy. Of all the hydrogen halides, HF has the shortest link length and also largest link dissociation energy.

Halogen Oxoacids

A halogen oxoacid is one acid v hydrogen, oxygen, and halogen atoms. The mountain of an oxoacid can be identified through analysis of the compound"s structure. The halogen oxoacids are provided below:

Hypochlorous Acid: HOCl Chlorous Acid: HClO2 Chloric Acid: HClO3 Perchloric Acid: HClO4 Hypobromous Acid: HOBr Bromic Acid: HBrO3 Perbromic Acid: HBrO4 Hypoiodous Acid: HOI Iodic Acid: HIO3 Metaperiodic Acid: HIO4; H5IO6

In each of these acids, the proton is bonded to an oxygen atom; therefore, comparing proton bond lengths is not advantageous in this case. Instead, electronegativity is the dominant factor in the oxoacid"s acidity. Acidic strength boosts with an ext oxygen atoms bound come the central atom.

States of issue at Room Temperature

Table 1.7: claims of Matter and Appearance of Halogens States of issue (at Room Temperature)Halogen Appearance
Solid Iodine Violet
Astatine Black/Metallic
Liquid Bromine Reddish-Brown
Gas Fluorine Pale Yellow-Brown
Chlorine Pale Green

Explanation because that Appearance

The halogens" color are outcomes of the absorption of visible light by the molecules, which reasons electronic excitation. Fluorine absorbs violet light, and therefore appears light yellow. Iodine, ~ above the various other hand, absorbs yellow light and also appears violet (yellow and also violet room complementary colors, which can be identified using a color wheel). The color of the halogens prosper darker under the group:

Fluorine → pale yellow/brown Chlorine → pale environment-friendly Bromine → red-brown www.crscientific.com/brominecell4.jpg Iodine → violet genbsci-ch.org.bsci-ch.org.wisc.edu/lab/PTL...ments/I/I.jpeg Astatine* → black/metallic www4.msu.ac.th/satit/studentP...t/astatine.jpg

In close up door containers, fluid bromine and also solid iodine space in equilibrium v their vapors, i m sorry can frequently be seen as colored gases. Back the color for astatine is unknown, the is assumed that astatine should be darker than iodine"s violet (i.e. Black) based on the preceding trend.

Oxidation says of Halogens in Compounds

As a general rule, halogens usually have actually an oxidation state of -1. However, if the halogen is bonded to oxygen or to an additional halogen, the can take on different states: the -2 preeminence for oxygen take away precedence end this rule; in the situation of two various halogens external inspection together, the an ext electronegative atom bring away precedence and adopts the -1 oxidation state.

Example 1.1: Iodine Chloride (ICl)

Chlorine has an oxidation state that -1, and iodine will have an oxidation that +1. Chlorine is more electronegative than iodine, therefore giving the the -1 oxidation state.


Oxygen has actually a full oxidation state that -8 (-2 fee x 4 atoms= -8 full charge). Hydrogen has a total oxidation state that +1. Including both that these worths together, the complete oxidation state that the compound so far is -7. Due to the fact that the final oxidation state of the compound must be 0, bromine"s oxidation state is +7.

One 3rd exception come the rule is this: if a halogen exist in the elemental type (X2), that oxidation state is zero.

Table 1.8: Oxidation says of Halogens HalogenOxidation claims in Compounds
Fluorine (always) -1*
Chlorine -1, +1, +3, +5, +7
Bromine -1, +1, +3, +4, +5
Iodine -1, +1,+5, +7
Astatine -1, +1, +3, +5, +7

Example 1.3: Fluorine

Why does fluorine constantly have one oxidation state of-1 in its compounds?


Electronegativity increases throughout a period, and decreases down a group. Therefore, fluorine has the greatest electronegativity of all of the elements, shown by its position on the periodic table. The electron construction is 1s​2 2s2 2p5. If fluorine gains one much more electron, the outermost p orbitals are fully filled (resulting in a full octet). Since fluorine has a high electronegativity, that can conveniently remove the preferred electron from a nearby atom. Fluorine is climate isoelectronic v a noble gas (with eight valence electrons); every its outermost orbitals are filled. Fluorine is much an ext stable in this state.

Applications that Halogens

Fluorine: return fluorine is an extremely reactive, it serves many industrial purposes. Because that example, it is a vital component the the plastic polytetrafluoroethylene (called Teflon-TFE through the DuPont company) and specific other polymers, regularly referred to together fluoropolymers. Chlorofluorocarbons (CFCs) are organic bsci-ch.orgicals that were supplied as refrigerants and propellants in aerosols prior to growing concerns around their feasible environmental impact led to your discontinued use. Hydrochlorofluorocarbons (HFCs) are currently used instead. Fluoride is also added to toothpaste and also drinking water to help reduce tooth decay. Fluorine also exists in the clay provided in some ceramics. Fluorine is connected with generating nuclear power as well. In addition, the is used to develop fluoroquinolones, which are antibiotics. Below is a perform of several of fluorine"s important inorganic compounds.

Table 1.9: crucial Inorganic link of Fluorine CompoundUses
Na3AlF6 Manufacture that aluminum
BF3 Catalyst
CaF2 Optical components, produce of HF, metallurgical flux
ClF3 Fluorinating agent, reprocessing atom fuels
HF Manufacture the F2, AlF3, Na3AlF6, and fluorocarbons
LiF Ceramics manufacture, welding, and also soldering
NaF Fluoridating water, dentist prophylaxis, insecticide
SF6 Insulating gas because that high-voltage electrical equipment
SnF2 Manufacture the toothpaste
UF6 produce of uranium fuel because that nuclear reactors

Chlorine: Chlorine has countless industrial uses. That is used to disinfect drinking water and also swimming pools. Salt hypochlorite (NaClO) is the main component of bleach. Hydrochloric acid, sometimes referred to as muriatic acid, is a typically used acid in industry and also laboratories. Chlorine is also present in polyvinyl chloride (PVC), and several other polymers. PVC is provided in wire insulation, pipes, and electronics. In addition, chlorine is really useful in the pharmaceutical industry. Medicinal assets containing chlorine are supplied to law infections, allergies, and also diabetes. The neutralized form of hydrochloride is a ingredient of countless medications. Chlorine is additionally used come sterilize hospital machinery and limit infection growth. In agriculture, chlorine is a component of plenty of commercial pesticides: DDT (dichlorodiphenyltrichloroethane) was used as an farming insecticide, but its usage was discontinued.

Bromine: Bromine is supplied in flame retardants because of that is fire-resistant properties. It additionally found in the pesticide methyl bromide, i beg your pardon facilitates the storage of crops and eliminates the spread of bacteria. However, the excessive use of methyl bromide has actually been discontinued due to its impact on the ozone layer. Bromine is affiliated in gasoline production as well. Other provides of bromine incorporate the production of photography film, the contents in fire extinguishers, and also drugs dealing with pneumonia and Alzheimer"s disease.

Iodine: Iodine is crucial in the proper functioning of the thyroid gland that the body. If the body does not receive adequate iodine, a goiter (enlarged thyroid gland) will certainly form. Table salt now has iodine to help promote proper functioning that the thyroid hormones. Iodine is additionally used as an antiseptic. Solutions provided to clean open up wounds most likely contain iodine, and also it is commonly found in disinfectant sprays. In addition, silver iodide is necessary for photography development.

Astatine: since astatine is radioactive and rare, there room no proven offers for this halogen element. However, there is speculation the this aspect could aid iodine in regulation the thyroid hormones. Also, 211At has been used in mice to assist the examine of cancer.

VII. External Links

Grube, Karl; Leffler, Amos J. "Synthesis of steel halides (ML)." J. bsci-ch.org. Educ. 1993, 70, A204. Elson, Jesse. "A bonding parameter. III, Water solubilities and also melting point out of the alkali halogens." J. bsci-ch.org. Educ.1969, 46, 86. Fessenden, Elizabeth. "Structural bsci-ch.orgistry that the interhalogen compounds." J. bsci-ch.org. Educ. 1951, 28, 619. Holbrook, Jack B.; Sabry-Grant, Ralph; Smith, Barry C.; Tandel, Thakor V. "Lattice enthalpies the ionic halides, hydrides, oxides, and also sulfides: Second-electron affinities of atomic oxygen and also sulfur." J. bsci-ch.org. Educ. 1990, 67, 304. Kildahl, Nicholas K. "A procedure for determining formulas for the straightforward p-block oxoacids." J. bsci-ch.org. Educ. 1991, 68, 1001. Liprandi, Domingo A.; Reinheimer, Orlando R.; Paredes, José F.; L"Argentière, Pablo C. "A Simple, Safe method To Prepare Halogens and also Study your Visual nature at a Technical an additional School." J. bsci-ch.org. Educ. 1999 76. Meek, terry L. "Acidities of oxoacids: Correlation through charge distribution."J. bsci-ch.org. Educ. 1992, 69, 270.

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Practice Problems

Why go fluorine constantly have an oxidation state that -1 in that is compounds? discover the oxidation state of the halogen in each problem: HOCl KIO3 F2 What space three offers of chlorine? i beg your pardon element(s) exist(s) together a heavy in room temperature? carry out the adhering to increase or decrease down the group of halogens? boiling point and melting point electronegativity ionization power


Electronegativity increases throughout a period, and decreases under a group. Therefore, fluorine has actually the highest electronegativity the end of all of the elements. Since fluorine has actually seven valence electrons, it only needs one an ext electron come acheive a noble gas construction (eight valence electrons). Therefore, it will be an ext likely come pull off an electron indigenous a nearby atom. disinfecting water, pesticides, and also medicinal commodities +1 (Hydrogen has an oxidation state that +1, and also oxygen has actually an oxidation state that -2. Therefore, chlorine must have actually an oxidation state that +1 so the the total charge deserve to be zero) +5 (Potassium"s oxidation state is +1. Oxygen has actually an oxidation state that -2, so because that this compound it is -6 (-2 charge x 3 atoms= -6). Since the total oxidation state has to be zero, iodine"s oxidation state must be +5). 0 (Elemental forms always have one oxidation state the 0.) iodine and astatine boosts decreases decreases


Hill, Graham, and John Holman. bsci-ch.orgistry in Context. Fifth ed. United Kingdom: Nelson Thornes, 2000. 224-25. Petrucci, Ralph H. Genereal bsci-ch.orgistry: principles and modern-day Applications. Nine Ed. Brand-new Jersey: Pearson education and learning Inc, 2007. 920-928. Verma, N.K., B. Kapila, and also S.K. Khanna. Considerable bsci-ch.orgistry XII. Brand-new Delhi: Laxmi Publications, 2007. 718-30.

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