Why halogens are diatomic

Bromine is also found in compounds called halons, which contain carbon atoms to which fluorine, fluorine, and sometimes chlorine, are also attached. These compounds are used in fire extinguishers, since they do not damage electronic equipment.

Methyl bromide, CH 3 Br, used to be used as a soil fumigant to kill insects and bacteria, but its use is being phased out under the Montreal Protocols. Iodine forms dark, shiny, purple crystals at room temperature. The name come from the Greek word iodes , meaning "violet. It is found in the ores iodargyrite [silver iodide, AgI] and lautarite [calcium iodate, Ca IO 3 2 ], in seawater, and some natural sea-salt deposits and brines. Iodine is toxic, but it is so much less reactive than the other halogens that it is not as dangerous, and in low concentrations it can be used as an antibacterial agent.

Iodine in the form of the iodide anion, I - is essential in the diet; it accumulates in the thyroid gland, where it is incorporated into hormones that help to regulate metabolic functions. Iodine deficiency results in a condition called goiter, in which the thyroid gland becomes enlarged.

Radioactive iodine, a beta emitter which decays to xenon with a half-life of 8 days, is used to diagnose thyroid problems. Silver iodide, AgI, is light-sensitive, and is used in photography; it is also used in seeding clouds to promote the formation of rain. Astatine is a radioactive element. The name of the element is derived from from the Greek word astatos , which means "unstable.

Astatine is found in trace amounts in some uranium ores, where it is produced as a part of the decay series of uranium and thorium, but since all of its isotopes have fairly short half-lives the longest, astatine, has a half-life of 8 hours , there is not much of this element around.

It is estimated that there is less than 30 grams of astatine in the Earth's crust. John Emsley, The Elements , 3rd edition. Oxford: Clarendon Press, Oxford: Oxford University Press, David L. Heiserman, Exploring Chemical Elements and their Compounds.

In contrast, monatomic elements consist of single atoms e. Diatomic compounds consist of two different elements. There are seven pure elements that form diatomic molecules. This is a list of the seven diatomic elements.

The seven diatomic elements are:. All of these elements are nonmetals, since the halogens are a special type of nonmetallic element. Bromine is a liquid at room temperature, while the other elements all gases under ordinary conditions.

As the temperature is lowered or pressure is increased, the other elements become diatomic liquids. Astatine atomic number 85, symbol At and tennessine atomic number , symbol Ts are also in the halogen group and may form diatomic molecules. However, some scientists predict tennessine may behave more like a noble gas.

While only these seven elements routinely form diatomic molecules, other elements can form them. However, diatomic molecules formed by other elements are not very stable, so their bonds are easily broken.

The elements ending with "-gen" including halogens form diatomic molecules. Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile. Hydrogen halides readily dissolve in water to form hydrohalic hydrofluoric , hydrochloric , hydrobromic , hydroiodic acids. The properties of these acids are given below:. It may seem counterintuitive to say that HF is the weakest hydrohalic acid because fluorine has the highest electronegativity.

A strong bond is determined by a short bond length and a large bond dissociation energy. Of all the hydrogen halides, HF has the shortest bond length and largest bond dissociation energy. A halogen oxoacid is an acid with hydrogen, oxygen, and halogen atoms. The acidity of an oxoacid can be determined through analysis of the compound's structure.

The halogen oxoacids are given below:. In each of these acids, the proton is bonded to an oxygen atom; therefore, comparing proton bond lengths is not useful in this case. Instead, electronegativity is the dominant factor in the oxoacid's acidity. Acidic strength increases with more oxygen atoms bound to the central atom. The halogens' colors are results of the absorption of visible light by the molecules, which causes electronic excitation.

Fluorine absorbs violet light, and therefore appears light yellow. Iodine, on the other hand, absorbs yellow light and appears violet yellow and violet are complementary colors, which can be determined using a color wheel.

The colors of the halogens grow darker down the group:. In closed containers, liquid bromine and solid iodine are in equilibrium with their vapors, which can often be seen as colored gases. Although the color for astatine is unknown, it is assumed that astatine must be darker than iodine's violet i.

As a general rule, halogens usually have an oxidation state of However, if the halogen is bonded to oxygen or to another halogen, it can adopt different states: the -2 rule for oxygen takes precedence over this rule; in the case of two different halogens bonded together, the more electronegative atom takes precedence and adopts the -1 oxidation state.

Chlorine is more electronegative than iodine, therefore giving it the -1 oxidation state. Adding both of these values together, the total oxidation state of the compound so far is One third exception to the rule is this: if a halogen exists in its elemental form X 2 , its oxidation state is zero.

Electronegativity increases across a period, and decreases down a group. Therefore, fluorine has the highest electronegativity of all of the elements, indicated by its position on the periodic table. If fluorine gains one more electron, the outermost p orbitals are completely filled resulting in a full octet. Because fluorine has a high electronegativity, it can easily remove the desired electron from a nearby atom. Fluorine is then isoelectronic with a noble gas with eight valence electrons ; all its outermost orbitals are filled.

Fluorine is much more stable in this state. Fluorine : Although fluorine is very reactive, it serves many industrial purposes. For example, it is a key component of the plastic polytetrafluoroethylene called Teflon-TFE by the DuPont company and certain other polymers, often referred to as fluoropolymers.

Chlorofluorocarbons CFCs are organic chemicals that were used as refrigerants and propellants in aerosols before growing concerns about their possible environmental impact led to their discontinued use. Hydrochlorofluorocarbons HFCs are now used instead. Fluoride is also added to toothpaste and drinking water to help reduce tooth decay.

Fluorine also exists in the clay used in some ceramics. Fluorine is associated with generating nuclear power as well. In addition, it is used to produce fluoroquinolones, which are antibiotics. Below is a list of some of fluorine's important inorganic compounds.

Chlorine : Chlorine has many industrial uses. It is used to disinfect drinking water and swimming pools. Sodium hypochlorite NaClO is the main component of bleach. Hydrochloric acid, sometimes called muriatic acid, is a commonly used acid in industry and laboratories.

Chlorine is also present in polyvinyl chloride PVC , and several other polymers. PVC is used in wire insulation, pipes, and electronics. In addition, chlorine is very useful in the pharmaceutical industry.

Medicinal products containing chlorine are used to treat infections, allergies, and diabetes. The neutralized form of hydrochloride is a component of many medications. Chlorine is also used to sterilize hospital machinery and limit infection growth. In agriculture, chlorine is a component of many commercial pesticides: DDT dichlorodiphenyltrichloroethane was used as an agricultural insecticide, but its use was discontinued.

Bromine : Bromine is used in flame retardants because of its fire-resistant properties. It also found in the pesticide methyl bromide, which facilitates the storage of crops and eliminates the spread of bacteria. However, the excessive use of methyl bromide has been discontinued due to its impact on the ozone layer.

Bromine is involved in gasoline production as well. Other uses of bromine include the production of photography film, the content in fire extinguishers, and drugs treating pneumonia and Alzheimer's disease. Iodine : Iodine is important in the proper functioning of the thyroid gland of the body. If the body does not receive adequate iodine, a goiter enlarged thyroid gland will form. Table salt now contains iodine to help promote proper functioning of the thyroid hormones.

Iodine is also used as an antiseptic. Solutions used to clean open wounds likely contain iodine, and it is commonly found in disinfectant sprays. In addition, silver iodide is important for photography development. Astatine : Because astatine is radioactive and rare, there are no proven uses for this halogen element.

However, there is speculation that this element could aid iodine in regulating the thyroid hormones. Also, At has been used in mice to aid the study of cancer. Elements Fluorine - Fluorine has an atomic number of 9 and is denoted by the symbol F.