ElementsHydrogen Halides and Halogen OxoacidsStates of matter at Room Temperature

The halogens are situated on the left of the noble gases on the periodic table. These five toxic, non-metallic aspects make up team 17 the the periodic table and also consist of: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Return astatine is radioactive and only has short-lived isotopes, that behaves similar to iodine and also is often consisted of in the halogen group. Since the halogen elements have 7 valence electrons, they just require one added electron to form a full octet. This characteristic provides them more reactive than other non-metal groups.

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Halogens kind diatomic molecule (of the type X2​, where X denotes a halogen atom) in their elemental states. The bonds in this diatomic molecules room non-polar covalent solitary bonds. However, halogens readily integrate with most elements and are never ever seen uncombined in nature. Together a general rule, fluorine is the most reactive halogen and also astatine is the least reactive. All halogens kind Group 1 salts with similar properties. In these compounds, halogens are current as halide anions v charge of -1 (e.g. Cl-, Br-, etc.). Replacing the -ine finishing with an -ide ending indicates the visibility of halide anions; for example, Cl- is named "chloride." In addition, halogens act as oxidizing agents—they exhibition the property to oxidation metals. Therefore, most of the stclairdrake.netical reactions that involve halogens room oxidation-reduction reaction in aqueous solution. The halogens often kind single bonds, as soon as in the -1 oxidation state, through carbon or nitrogen in essential compounds. Once a halogen atom is substituted because that a covalently-bonded hydrogen atom in an essential compound, the prefix halo- deserve to be supplied in a basic sense, or the prefixes fluoro-, chloro-, bromo-, or iodo- can be provided for certain halogen substitutions. Halogen aspects can cross-link to type diatomic molecules with polar covalent solitary bonds.

Chlorine (Cl2) to be the an initial halogen to be uncovered in 1774, complied with by iodine (I2), bromine (Br2), fluorine (F2), and astatine (At, discovered last in 1940). The name "halogen" is obtained from the Greek roots hal- ("salt") and also -gen ("to form"). With each other these words incorporate to median "salt former", express the truth that halogens kind salts when they react with metals. Halite is the mineral surname for absent salt, a organic mineral consisting basically of sodium chloride (NaCl). Lastly, the halogens are also relevant in everyday life, whether it be the fluoride that goes in toothpaste, the chlorine that disinfects drinking water, or the iodine the facilitates the production of thyroid hormone in one"s body.


Fluorine - Fluorine has an atomic variety of 9 and is denoted through the price F. Elemental fluorine was an initial discovered in 1886 by isolating that from hydrofluoric acid. Fluorine exists together a diatomic molecule in its cost-free state (F2) and also is the many abundant halogen uncovered in the Earth"s crust. Fluorine is the many electronegative element in the periodic table. It appears as a pale yellow gas at room temperature. Fluorine also has a fairly small atom radius. That oxidation state is constantly -1 other than in that is elemental, diatomic state (in i m sorry its oxidation state is zero). Fluorine is very reactive and also reacts straight with all facets except helium (He), neon (Ne) and also argon (Ar). In H2O solution, hydrofluoric mountain (HF) is a weak acid. Although fluorine is highly electronegative, that is electronegativity does not identify its acidity; HF is a weak acid as result of the truth that the fluoride ion is basic (pH>7). In addition, fluorine to produce very an effective oxidants. For example, fluorine have the right to react v the noble gas xenon and form the solid oxidizing certified dealer Xenon Difluoride (XeF2). Over there are many uses for fluorine, which will certainly be discussed in part VI that this article.

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

Bromine - Bromine has an atomic number of 35 through a prize of Br. That was very first discovered in 1826. In its element form, that is the diatomic molecule Br2. At room temperature, bromine is a reddish- brown liquid. That oxidation states vary from -1, +1, 3, 4 and 5. Bromine is an ext reactive than iodine, but not together reactive together chlorine. Also, bromine has two isotopes: 79Br and 81Br. Bromine is composed of bromide salts, which have been discovered in the sea. The world production the bromide has increased substantially over the years, because of its access and longer existence. Like all of the other halogens, bromine is one oxidizing agent, and is very toxic.

Iodine - Iodine has actually 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 actually one secure isotope: 127I. That was first discovered in 1811 with the usage of seaweed and also sulfuric acid. Currently, iodide ions deserve to be isolated in seawater. Return iodine is not very soluble in water, the solubility may rise if certain iodides are blended in the solution. Iodine has plenty of important duties in life, including thyroid hormone production. This will certainly be disputed in part VI that the text.

Astatine - Astatine is a radioactive facet with one atomic variety of 85 and symbol At. Its feasible oxidation states include: -1, +1, 3, 5 and 7. The is the just halogen that is not a diatomic molecule and it appears as a black, metallic solid at room temperature. Astatine is a really rare element, so there is not that lot known around this element. In addition, astatine has a really short radioactive half-life, no much longer than a pair of hours. It was discovered in 1940 by synthesis. Also, that is believed that astatine is similar to iodine. However, these two elements are presume to different 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 clues (increases down the group)

The melting and also boiling points rise down the group because of the van der Waals forces. The size of the molecules rises down the group. This increase in size means an boost in the stamin of the valve der Waals forces.

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

Atomic Radius (increases under the group)

The dimension of the nucleus boosts down a team (F due to the fact that the numbers of protons and neutrons increase. In addition, more energy level are included with every period. This results in a bigger orbital, and also therefore a much longer atomic radius.

Table 1.3: atom Radii of 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 down the group)

If the outer valence electrons are not near the nucleus, it does not take as much power to eliminate them. Therefore, the power required to pull turn off the outermost electron is not as high because that the elements at the bottom of the group because there are much more energy levels. Also, the high ionization energy makes the element appear non-metallic. Iodine and also astatine display screen metallic properties, therefore ionization energy decreases under the team (At Table 1.4 Ionization energy of Halogens Halogen First Ionization power (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 boosts down the group because of the boost in power levels at increasingly lower levels. The electrons room progressively further from the nucleus; therefore, the nucleus and also the electrons room not together attracted to every other. Boost in shielding is observed. Electronegativity as such decreases down the group (At Table 1.5: Electronegativity of 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 atomic size boosts down the group, electron affinity normally decreases (At Cl). One electron will not be as attracted to the nucleus, bring about a low electron affinity. However, fluorine has a lower electron affinity 보다 chlorine. This deserve to be described by the tiny size of fluorine, contrasted to chlorine.

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

Reactivity of aspects (decreases under the group)

The reactivities of the halogens decrease under the team ( in ~ Cl atom radius rises in dimension with boost of digital energy levels. This lessens the attraction for valence electron of various other atoms, to decrease reactivity. This decrease additionally occurs since electronegativity decreases under a group; therefore, there is much less electron "pulling." In addition, over there is a diminish in oxidizing capacity down the group.

Hydrogen Halides

A halide is formed when a halogen reacts with another, much less electronegative element to kind a binary compound. Hydrogen, for example, reacts with halogens to type halides that the form HX:

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

Hydrogen halides conveniently dissolve in water to type hydrohalic (hydrofluoric, hydrochloric, hydrobromic, hydroiodic) acids. The nature of this acids are given below:

The mountain are formed by the adhering to reaction: HX (aq) + H2O (l) → X- (aq) + H3O+ (aq) all hydrogen halides kind strong acids, except HF The acidity of the hydrohalic acids increases as follows: HF

Hydrofluoric acid can etch glass and particular inorganic fluorides over a long duration of time.

It might seem counterintuitive come say the HF is the weakest hydrohalic acid due to the fact that fluorine has the highest electronegativity. However,​ the H-F bond is really strong; if the H-X link is strong, the resulting mountain is weak. A solid bond is determined by a brief bond length and also a large bond dissociation energy. Of all the hydrogen halides, HF has the shortest bond length and largest bond dissociation energy.

Halogen Oxoacids

A halogen oxoacid is one acid v hydrogen, oxygen, and halogen atoms. The mountain of one oxoacid have the right to be figured out through evaluation of the compound"s structure. The halogen oxoacids are given 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 every of this acids, the proton is external inspection to one oxygen atom; therefore, to compare proton bond lengths is not useful in this case. Instead, electronegativity is the leading factor in the oxoacid"s acidity. Acidic strength increases with an ext oxygen atoms bound to 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 for Appearance

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

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

In closed containers, fluid bromine and also solid iodine space in equilibrium with their vapors, i beg your pardon can often be viewed as colored gases. Although the color for astatine is unknown, the is assumed that astatine must be darker than iodine"s violet (i.e. Black) based on the coming before trend.

Oxidation states of Halogens in Compounds

As a general rule, halogens usually have actually an oxidation state the -1. However, if the halogen is external inspection to oxygen or to an additional halogen, that can embrace different states: the -2 ascendancy for oxygen takes precedence end this rule; in the instance of two different halogens bonded together, the much more electronegative atom takes precedence and also adopts the -1 oxidation state.

Example 1.1: Iodine Chloride (ICl)

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


Oxygen has a complete oxidation state of -8 (-2 charge x 4 atoms= -8 complete charge). Hydrogen has actually a full oxidation state that +1. Adding both the these worths together, the full oxidation state the the link so far is -7. Since the last oxidation state that the compound need to be 0, bromine"s oxidation state is +7.

One 3rd exception to the rule is this: if a halogen exists in that is elemental kind (X2), its oxidation state is zero.

Table 1.8: Oxidation states 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 walk fluorine constantly have an oxidation state of-1 in that compounds?


Electronegativity increases throughout a period, and decreases under a group. Therefore, fluorine has actually the greatest electronegativity of every one of the elements, suggested by its position on the routine table. That electron construction is 1s​2 2s2 2p5. If fluorine profit one much more electron, the outermost ns orbitals are totally filled (resulting in a complete octet). Because fluorine has actually a high electronegativity, it can quickly remove the preferred electron indigenous a surrounding atom. Fluorine is then 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 of Halogens

Fluorine: although fluorine is really reactive, that serves numerous industrial purposes. For example, the is a vital component that the plastic polytetrafluoroethylene (called Teflon-TFE by the DuPont company) and details other polymers, regularly referred to as fluoropolymers. Chlorofluorocarbons (CFCs) are organic stclairdrake.neticals that were offered as refrigerants and also propellants in aerosols prior to growing concerns around their possible environmental affect led to their discontinued use. Hydrochlorofluorocarbons (HFCs) are currently used instead. Fluoride is also included to toothpaste and also drinking water to aid reduce tooth decay. Fluorine also exists in the clay provided in part ceramics. Fluorine is associated with generating nuclear power as well. In addition, the is used to produce fluoroquinolones, which room antibiotics. Listed below is a perform of few of fluorine"s essential inorganic compounds.

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

Chlorine: Chlorine has many industrial uses. The is provided to disinfect drink water and also swimming pools. Salt hypochlorite (NaClO) is the key component of bleach. Hydrochloric acid, sometimes called muriatic acid, is a frequently used mountain in industry and also laboratories. Chlorine is likewise present in polyvinyl chloride (PVC), and also several other polymers. PVC is provided in cable insulation, pipes, and also electronics. In addition, chlorine is an extremely useful in the medicine industry. Medicinal commodities containing chlorine are offered to law infections, allergies, and diabetes. The neutralized kind of hydrochloride is a component of many medications. Chlorine is likewise used come sterilize hospital machinery and also limit epidemic growth. In agriculture, chlorine is a ingredient of countless commercial pesticides: DDT (dichlorodiphenyltrichloroethane) was offered as an farming insecticide, but its usage was discontinued.

Bromine: Bromine is supplied in fire retardants due to the fact that of the fire-resistant properties. It additionally found in the pesticide methyl bromide, i m sorry facilitates the warehouse of crops and also eliminates the spread of bacteria. However, the too much use the methyl bromide has been discontinued as result of its influence on the ozone layer. Bromine is associated in gasoline production as well. Other offers of bromine incorporate the manufacturing of photography film, the content in fire extinguishers, and also drugs treating pneumonia and Alzheimer"s disease.

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

Astatine: because astatine is radioactive and also rare, there are no proven offers for this halogen element. However, there is speculation that this facet could aid iodine in regulation the thyroid hormones. Also, 211At has actually been used in mice to help the study of cancer.

VII. Exterior Links

Grube, Karl; Leffler, Amos J. "Synthesis of steel halides (ML)." J. stclairdrake.net. Educ. 1993, 70, A204. Elson, Jesse. "A bonding parameter. III, Water solubilities and melting point out of the alkali halogens." J. stclairdrake.net. Educ.1969, 46, 86. Fessenden, Elizabeth. "Structural stclairdrake.netistry that the interhalogen compounds." J. stclairdrake.net. 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 six of atomic oxygen and also sulfur." J. stclairdrake.net. Educ. 1990, 67, 304. Kildahl, Nicholas K. "A procedure for determining formulas because that the simple p-block oxoacids." J. stclairdrake.net. Educ. 1991, 68, 1001. Liprandi, Domingo A.; Reinheimer, Orlando R.; Paredes, José F.; L"Argentière, Pablo C. "A Simple, Safe means To Prepare Halogens and Study your Visual properties at a Technical secondary School." J. stclairdrake.net. Educ. 1999 76. Meek, terrycloth L. "Acidities the oxoacids: Correlation with charge distribution."J. stclairdrake.net. Educ. 1992, 69, 270.

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Practice Problems

Why does fluorine always have an oxidation state the -1 in that is compounds? discover the oxidation state that the halogen in every problem: HOCl KIO3 F2 What space three supplies of chlorine? i m sorry element(s) exist(s) together a heavy in room temperature? perform the complying with increase or decrease under the group of halogens? boiling allude and melting point electronegativity ionization energy


Electronegativity increases throughout a period, and also decreases under a group. Therefore, fluorine has actually the greatest electronegativity out of all of the elements. Because fluorine has actually seven valence electrons, that only needs one more electron come acheive a noble gas construction (eight valence electrons). Therefore, it will be much more likely to pull off an electron native a surrounding atom. disinfecting water, pesticides, and medicinal commodities +1 (Hydrogen has an oxidation state the +1, and also oxygen has actually an oxidation state of -2. Therefore, chlorine must have an oxidation state the +1 so the the complete charge have the right to be zero) +5 (Potassium"s oxidation state is +1. Oxygen has an oxidation state the -2, so for this link it is -6 (-2 fee x 3 atoms= -6). Since the total oxidation state needs to be zero, iodine"s oxidation state have to be +5). 0 (Elemental forms always have one oxidation state of 0.) iodine and also astatine increases decreases reduce


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

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