Science Fair Project Encyclopedia
|Name, Symbol, Number||bromine, Br, 35|
|Group, Period, Block||17 (VIIA), 4, p|
|Density, Hardness||3119 kg/m3 (300 K), NA|
|Appearance|| Gas: red-brown |
solid: metallic luster
|Atomic weight||79.904 amu|
|Atomic radius (calc.)||115 (94) pm|
|Covalent radius||114 pm|
|van der Waals radius||185 pm|
|Electron configuration||[Ar]3d10 4s24p5|
|e- 's per energy level||2, 8, 18, 7|
|Oxidation states (Oxide)||±1,5 (strong acid)|
|State of matter||Liquid (nonmagnetic)|
|Melting point||265.8 K (-7.2°C/19°F)|
|Boiling point||332 K (59°C/138°F)|
|Molar volume||19.78 ×10-6 m3/mol|
|Heat of vaporization||15.438 kJ/mol|
|Heat of fusion||5.286 kJ/mol|
|Vapor pressure||5800 Pa at 280.1 K|
|Speed of sound||206 m/s at 293.15 K|
|Electronegativity||2.96 (Pauling scale)|
|Specific heat capacity||480 J/(kg*K)|
|Electrical conductivity||no data|
|Thermal conductivity||0.122 W/(m*K)|
|1st ionization potential||1139.9 kJ/mol|
|2nd ionization potential||2103 kJ/mol|
|3rd ionization potential||3470 kJ/mol|
|4th ionization potential||4560 kJ/mol|
|5th ionization potential||5760 kJ/mol|
|6th ionization potential||8550 kJ/mol|
|7th ionization potential||9940 kJ/mol|
|8th ionization potential||18600 kJ/mol|
|Most stable isotopes|
|SI units & STP are used except where noted.|
Bromine (from Gr. Bromos, meaning "stench"), is a chemical element in the periodic table that has the symbol Br and atomic number 35. A halogen element, bromine is a red volatile liquid at room temperature which has a reactivity between chlorine and iodine. This element is harmful to human tissue in a liquid state and its vapor irritates eyes and throat.
Bromine is the only liquid nonmetallic element at room temperature. It is a heavy, mobile, reddish-brown liquid, that evaporates easily at standard temperature and pressures in a red vapor (its color resembles nitrogen dioxide) that has a strong disagreeable odor resembling that of chlorine. A halogen, bromine resembles chlorine chemically but is less active (it is more active than iodine however). Bromine is slightly soluble in water, and highly soluble in carbon disulfide aliphatic alcohols (such as methanol) and acetic acid. It bonds easily with many elements and has a strong bleaching action.
Bromine is highly reactive and is a powerful oxidizing agent in the presence of water. It reacts vigorously with amines, alkenes and phenols as well as aliphatic and aromatic hydrocarbons, ketones and acids (these are brominated by either addition or substitution). With many of the metals and elements, anhydrous bromine is less reactive than wet bromine; however, dry bromine reacts vigorously with aluminium, titanium, mercury as well as alkaline earth and alkaline metals.
Elemental bromine is used to manufacture a wide variety of bromine compounds used in industry and agriculture. Traditionally the largest use of bromine was in the production of 1,2-Dibromoethane which in turn was used as a gasoline anti-knock agent for leaded gasolines before they were largely phased out due to environmental considerations.
Bromine is also used in making fumigants, flameproofing agents, water purification compounds, dyes, medicinals, sanitizes, inorganic bromides for photography, etc. It is also used to form intermediates in organic synthesis, where it is preferred to iodine due to its much lower cost.
- When added to an alkene it will lose its color as it reacts forming a colorless bromoalkane.
- When added to phenol a white precipitate (2,4,6-tribromophenol ) will form.
Bromine occurs in nature as bromide salts in very diffuse amounts in crustal rock. Due to leaching bromide salts have accumulated in sea water (85 ppm), and may be economically recovered from brine wells and the Dead Sea (up to 5000 ppm).
Elemental bromine is a strong irritant and, in concentrated form, will produce painful blisters on exposed skin and especially mucous membranes. Even low concentrations of bromine vapor (from 10 ppm) can affect breathing, and inhalation of significant amounts of bromine can seriously damage the respiratory system.
Accordingly, one should always wear safety goggles and ensure adequate ventilation when handling bromine.
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