Bromine

Bromine
General Info
Atomic Symbol	Atomic symbol::Br
Atomic Number	Atomic number::35
Atomic Weight	Atomic weight::79.904 g/mol
Chemical series	halogen
Appearance	Reddish-brown
Group, Period, Block	17,4,p
Electron configuration	[Ar] 3d10, 4s2, 4p5
Electrons per shell	2,8,18,7
CAS number	CAS number::7726-95-6
Physical properties
Phase	Liquid
Density	Density::3.119 g/ml
Melting point	Melting point::265.95K
Boiling point	Boiling point::331.93K
Isotopes of Bromine
iso NA half-life DT DE (MeV) DP 67Br syn unrecorded α 7.32 68Br syn 1.2 µs α 2.107 69Br syn 24 ns α 3.78 70Br syn 79.1(8) ms α 9.28 70mBr syn 2.2(2) s α 9.31 71Br syn 21.4(6) s α 8.03 72Br syn 78.6(24) s α 41.77 72mBr syn 10.6(3) s α 6.89 73Br syn 3.4(2) min α 9.34 74Br syn 25.4(3) min α 9.15 74mBr syn 46(2) min α 18.07 75Br syn 96.7(13) min α 8.62 76Br syn 16.2(2) h α 9.25 76mBr syn 1.31(2) s α 9.31 77Br syn 57.036(6) h α 0.07 77mBr syn 4.28(10) min α 9.60 78Br syn 6.46(4) min α 10.00 79Br 50.69% is stable with α neutrons. 79mBr syn 4.86(4) s α 11.14 80Br syn 17.68(2) min α 9.21 80mBr syn 4.4205(8) h α 57.11 81Br 49.31% is stable with α neutrons. 82Br syn 35.282(7) h α 7.30 83Br syn 2.40(2) h α 40.13 84Br syn 31.80(8) min α 8.10 84mBr syn 6.0(2) min α 41.09 85Br syn 2.90(6) min α 72.53 86Br syn 55.1(4) s α 21.14 87Br syn 55.65(13) s α 27.83 88Br syn 16.29(6) s α 11.82 89Br syn 4.40(3) s α 9.83 90Br syn 1.91(1) s α 10.94 91Br syn 541(5) ms α 26.54 92Br syn 0.343(15) s α 107.63 93Br syn 102(10) ms α 79.02 94Br syn 70(20) ms α 53.41 95Br syn 150 ns α 21.03 96Br syn 259 ns α 35.81 97Br syn 300 ns α 39.02 98Br syn 634 ns α 127.63
All properties are for STP unless otherwise stated.

Bromine is a chemical element classified as a halogen and known by the chemical symbol Br. It is the only nonmetal element that remains liquid under normal conditions. Bromine is a reddish-brown color with a vapor of similar color and a horrible odor. Bromine is similar to other halogens, but quite unordinary and unique among all the elements.

Though used much more frequently a few decades ago, Bromine is used commercially throughout the world today. In gas and liquid form, Bromine is toxic to human skin, eyes, and throat, but is also useful in many ways that benefits humans. Though useful and used a lot, Bromine does not occur naturally and is hard to find in nature, most often appearing as Bromine salts in crustal rock.

Properties

Bromine appears as a reddish-brown liquid, at proper temperature, with a similarly colored vapor and a horrible odor. It stands as the only nonmetal element that exists as a liquid under ordinary conditions, also evaporating as a red vapor at standard temperature with a strong offensive odor resembling that of Chlorine. Chemically, Bromine appears less appealing than Chlorine and Fluorine, but is far more active than Iodine. Bromine compounds are very similar to the compounds of other halogens. Bromine is also soluble in organic solvents and in water, and will dissolve. Bromine may also react with water, creating hydro bromic acid.

Atomically, each Bromine atom contains 35 protons, corresponding with its number on the periodic table of elements. There are 47 variations of Bromine, also known as bromine isotopes, and 29 of them are radioactive. Each bromine isotope is marked by the number of neutrons in each atom, all of which are different. Along with the 47 bromine isotopes, there are 16 bromine isomers, which differ structurally.

Occurrences

Bromine Salts in the Dead Sea

Free elemental Bromine does not occur naturally, but exists exclusively as bromide salts diffused in crustal rock. Bromide salts have accumulated in sea water at over sixty five ppm (parts per million), which is far less than Chloride. It may be recovered from bromide-rich brine wells and from the waters of the Dead Sea. It exists in the Earth's crust at a concentration of about 0.4 ppm, placing it as the 62nd most abundant element. In soil, the bromine concentration normally varies between 5 and 40 ppm, skyrocketing to a concentration of about 500 ppm in volcanic soil.

The concentration of bromine in the atmosphere is terribly low, coming in at only a few ppt (parts per notation). However, many organobromine compounds can be found in small amounts in nature. China, Israel, and the U.S. all possess large bromine reserves; the U.S. laying claim to the largest.

Uses

Bromine Tablets used to purify drinking water

There are several industrial uses for Bromine; most are produced from Bromine but some are produced from Hydrogen bromide, made by burning Hydrogen in Bromine. The largest commercial use of Bromine is brominated flame retardants. These brominated flame retardants, when burned, produce hydro bromic acid to interfere with the chain reaction of oxidation in the fire. Many gaseous brominated halomethane compounds are non-toxic and make superior fire suppressants by acting directly with radical reactions to terminate the free radical chain reactions of combustion. These are most effectively used in confined spaces like submarines, airplanes, and space crafts; but due to expense and production their use has been greatly decreased. Bromochloromethane, bromochlorodifluoromethane, and bromotrifluoromethane are still used in aerospace and militant fire suppression.

The second most important use of bromine is water purification, as an alternative to chlorine. Brominated compounds are used in swimming pools and hot tubs for water treatment and to control algae and bacterial growth in industrial processes. Ethylene bromide was a popular gasoline additive in the 1970s, but its use has greatly decreased due to environmental control. Deadly methyl bromide was a widely used pesticide, to fumigate soil and housing by tenting, but due to the Montreal Protocol on Substances that Deplete the Ozone they have not been used since 2005. In the 19th and 20th centuries, bromide compounds were often used as sedatives. In 1975, the U.S. Food and Drug Administration removed bromide from over-the-counter sedatives. Today, simple salt bromides are used as anticonvulsants in veterinary and human medicine throughout the world.

Bromine in Ozone Depletion

Since the 1970s, the ozone layer has decreased about four percent in volume every decade. Bromine is one of the many contributors to this major decline. Bromine and Chlorine are two of the most commonly known factors of this major decline. Though Chlorine concentrations in the stratosphere are much larger than Bromine concentrations, about 150 times larger, Bromine is 97 times as damaging to the ozone layer as Chlorine is. The reason for this is that, even though there is not really a stable reserve for Bromine in the stratosphere, Hydrogen Bromide and Bromine Nitrate are easily photolyzed so that Bromine is almost always in a form that can react with the ozone layer. So, because of this, even though Bromine concentration levels are much lower that that of Chlorine and often considered less important, Bromine is still a major contributor to ozone depletion and should always be taken into account. However, one of the main processes in which Bromine damages the ozone layer involves Chlorine. So if the stratospheric Chlorine concentration levels were to decrease, in turn, the Bromine pathways to damaging the ozone layer would be slowed down. Though truly, it is not the process that causes the most damage, but the atom itself. One Bromine atom can destroy about 300,000 ozone atoms before being removed from the stratosphere. This negative effect on the ozone layer is one of the major reasons for the decrease in Bromine usage since the 1960s.

Video

The Discovery of Bromine