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Free bromine as element Br and as molecule Br2 do not occur in nature, but as colorless soluble mineral halide salts (for example table salt). The high solubility of bromide ions in water causes accumulation of these salts in the oceans via rivers.
Bromine is poisonous to humans. Even a little can cause a sore throat, shortness of breath and dizziness when inhaled, ingestion can lead to abdominal cramps and the vapor is corrosive to the eyes.
Place of bromium in the periodic table
Bromine is a chemical element with the symbol Br and atomic number 35. The element belongs to the group of halogens. As an element it forms diatomic molecules dibromine (Br2), a substance that does not occur naturally on Earth.
The element occurs in the form of easily soluble crystalline halide salts (bromine-halogen salts), mainly bromides and bromates. Due to the easy solubility of bromide ions in water, they are eventually carried by the rivers to the sea, where an accumulation of these salts takes place. This applies to all halogen salts hence the salty water of the oceans.
General properties of bromium
| Name | Symbol | Atomic number | Group | Period | Block | Series | Colour |
| Bromine, Bromium | Br | 35 | Halogens | Period 4 | P block | Halogens | Brown |
Chemical properties of bromium
| Atomic mass (u) | Electron configuration | Oxidation states | Electronegativity (Pauling) | Atomic radius (pm) Van der Waals radius (pm) | ionization potential (kJ.mol−1) |
| 79,904 | [Ar]3d10 4s2 4p5 | -1, +1, +5 | 2.96 | 114 185 | 1st: 1139.87 2nd: 2103.40 3rd: 3473.50 |
Physical properties of bromium
| Density ) | Melting point (K) | Boiling point (K) | Aggregation state |
Heat of fusion (kJ.mol−1) |
Heat of vaporization (kJ.mol−1) | Crystal structure | Specific heat (J.kg−1•K−1) | Heat conduction (Wm−1•K−1) |
| 3119 | 266 | 332 | Liquid | 5,286 | 15,438 | Orthorhombic? | 473 | 0.12 |
Isotopes of bromium
Bromine has two stable isotopes, 79Br (50.69%) and 81Br (49.31%). There are approximately 23 radioisotopes. Many bromine isotopes are a fission product of other atoms. Many of these bromine isotopes are delayed neutron emitters, an important property for controlling the rate of the chain reaction in a nuclear reactor. The radioactive isotopes of bromine have a short half-life.
The most stable isotopes of bromium
| Isotope | RA(%) | Half-life | Decay via | Decay energy(MeV) | Decay products |
| 76Br | Synthetic | 16.2 hours | ß+ | 4,963 | 76Se |
| 77Br | Synthetic | 57.04 hours | ß+ | 1,365 | 77Se |
| 78Br | Synthetic | 6.46 minutes | ß+ | 3,574 | 78Se |
| 79Br | 50.69 | Stable with 44 neutrons |
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| 80Br | Synthetic | 17.7 mins. | ß- ß+ | 2,004 1,871 | 80Kr 80Se |
| 81Br | 49.31 | Stable with 46 neutrons |
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| 82Br | Synthetic | 36 hours | ß- | 3,093 | 82Kr |
| 83Br | Synthetic | 2.4 hours | ß- | 3,896 | 83Kr |
The occurrence of Bromium
Bromine occurs naturally in bromides, which occur in low concentrations in seawater. Potassium bromide and potassium bromate are also found in salt mines.
Bromine production is six times the production of 1960. More than 500,000 tons of bromine are extracted annually. The main producers are the United States, China and Israel.
Bromine only occurs as bromide salts in the Earth’s crust. Flushing has caused bromide salts to accumulate in seawater to approximately 65 parts per million (ppm).
Bromine can be extracted economically from bromide-rich brine sand from the Dead Sea. The bromine concentration in soil varies between 5 and 40 (ppm), but volcanic soil can contain up to 500 (ppm). The concentration of bromine in the atmosphere is low.
Marine organisms are an important source of organobromine compounds (organic bromine compounds). More than 1500 compounds have been identified. The most common is methyl bromide (CH3 Br), of which approximately 50,000 tons per year is produced by marine algae. Hawaiian algae essential oil contains 80% Bromoform (tribromomethane).
Notable properties of bromium
Bromine is the only nonmetallic element that is liquid at room temperature and atmospheric pressure, and evaporates easily. The red-brown vapor has a characteristic odor. Bromine is very soluble in water and carbon disulfide. Like the other halogens, it reacts with many elements.
Inorganic
Inorganic bromine occurs naturally in the environment, but humans have added large amounts of bromine to the environment. People ingest inorganic bromine through food and drinking water, which can damage the nervous system and thyroid gland. Like other halogens, bromide ions are colorless and highly soluble in water.
Bromine reacts violently and explosively with aluminum metals, forming aluminum bromide:
- 2 Al + 3 Br2 → 2 AlBr3
Bromine reacts with hydrogen in gaseous form to give hydrogen bromide:
- H2 + Br2 → 2HBr
Bromine reacts with alkali metal iodides (displacement reaction). This reaction forms alkali metal bromide and forms the element iodine:
- 2 Nal + Br2 → 2 NaBr + I2
- 2 KI + Br2 → 2 KBr + I2