Iodine Element Properties and Information
Iodine Element Properties and Information
Iodine is 53rd element on the periodic table. Elements are arranged in the periodic table on the basis of the atomic number. Atomic number is the number of protons in the nucleus of the atom. Iodine has an atomic number of 53. It is located in the Group 17 and Period 5 of the periodic table of elements. It is denoted by I. The name is derived from the Greek word ‘Iodes’ which means Violet.
Bernard Courtois used to manufacture saltpetre using seaweed hash in early 1800s. In 1811, he added sulfuric acid and observed purple fumes which upon condensing formed crystals with metallic luster. He assumed that this is a new element. He sent samples to two chemists for further investigation and they independently confirmed that it was indeed a new element which has never been seen before.
Iodine is mainly found in seawater, it is present in the form of iodide and it amounts to 0.05 ppm. It is difficult to extract iodine directly using sea water. Historically, seaweeds would absorb iodine and it is through seaweed that iodine was obtained. Now a days, iodine is extracted from the natural brine deposits left by the evaporated ancient seas.
Physical Properties
- Iodine is a semi-lustrous, non-metallic, solid.
- The atomic mass of iodine is 126.9
- The melting point of iodine is 114°C
- The boiling point of iodine is 184°C
- The density of iodine is 4930 in S.I. units at 20°C
- Iodine is least volatile among all halogens.
- Iodine is heaviest among all halogens which is also stable.
- Upon heating at standard conditions, iodine forms violet liquid and violet vapour.
- Elemental iodide is slightly soluble in water.
- The melting and boiling point of iodine are highest among all halogens.
- Iodine is a semiconductor in the plane of its crystalline layers and an insulator in the perpendicular direction.
- Iodine has only 1 naturally occurring isotope and 36 radioactive isotopes.
Chemical Properties
- Among all halogens, iodine has the lowest; electronegativity, first ionisation energy, and electron affinity.
- Iodine is reactive in nature but compared to other halogens it is less reactive.
- Iodination of metals tends to result in lower oxidation state ccompounds when compared to chlorination or bromination.
- Iodine forms hydrides, halides, oxides, oxoacids, and organoiodine compounds as well.
Methods of Production
Brine source: The brine is first purified after being taken from the source. It is then acidified and the iodide present in it is oxidised to iodine using chlorine. The iodine solution obtained in this manner is dilute and it needs to be oxidised. The solution is concentrated by blowing air to evaporate the iodine. It is then passed to an absorbing tower where sulfur dioxide reduces the iodine. The hydrogen iodine is then reacted with chlorine to precipitate the iodine. The precipitated iodine is further purified and ready to be brought to market.
Relevance in Chemical and Related Industries
Iodine compounds: About 50% of iodine produced worldwide goes into manufacture of organo-iodine compounds. About 30% of iodine produced worldwide goes into manufacture of inorganic iodine compounds. Among the 30%, about 15% of iodine produced worldwide goes into manufacture of potassium iodide alone. The iodine compounds are used as catalysts, dyes, stabilisers, colourants, pharmaceuticals, inhibitors, etc.
Relevance in Other Industries
- Chemical analysis: The iodide and iodate anions are used for qualitative analysis, as in iodometry.
- Medicine: Elemental iodide is used as an antiseptic. Iodine’s antimicrobial activity is quick and works at low concentrations thus it is used in operating theatre.
Health Effects on Exposure
- Deficiency & accumulation: Iodine is an important element which plays it’s role in smooth function of thyroid gland. Deficiency of iodine causes swelling in thyroid gland. Also, large amounts of iodine is harmful to the thyroid gland because it will overactive it which causes disturbed heart beat.
- Toxic: Elemental iodide is toxic in nature. Since it is in gaseous form. The exposure will irritate eyes and lungs. Long time exposure can even damage the organs.
Effects on Surroundings
- Soil: The iodine in air can combine with water particles. The particles can seep into the soil wherein the iodine can bind to organic matter. If the concentration of iodine in that soil increases more than permissible amount then animals and human who eat crops grown from the soil can get affected.
- Radioactivity: Accidents in nuclear power plant causes large amounts of radioactive isotopes of iodine to get released into the atmosphere. One radioactive isotope has a half-life of millions of years. Such releases are harmful to surroundings.
References:
https://en.m.wikipedia.org/wiki/Iodine
