When two oxygen atoms come together they share two pairs of electrons between them, resulting in a double bond and a complete octet for each atom. Oxygen, O2 The double bond is shown conventionally by two lines joining the atoms. Each line represents one pair of shared electrons. Hydrogen has 1 electron in its valence shell and need 1 more electron to fulfill its octet. Oxygen has atomic number 8 hence it has 6 electrons in its outer most shell or valence shell thus it needs only two more electrons for octet.
Because its Octet gets completed by Double Bond hence no requirement for triple or Quadruple bond. Which molecule will have the strongest bond? A nitrogen molecule has a triple bond, while the rest have double or single bonds. In order to separate bonded atoms, a certain amount of energy is required. The more energy required, the stronger the bond. Ion-dipole forces are the strongest of the intermolecular forces.
Hydrogen bonding is a specific term for a particularly strong dipole-dipole interaction between a hydrogen atom and a very electronegative atom oxygen, fluorine, or nitrogen. However, hydrogen bonds are still not as strong as ion-dipole interactions. The bond length of carbon-carbon C-C in diamonds is pm.
The average length of a single carbon-carbon bond is commonly considered, but it is also the highest bond length that occurs for ordinary carbon covalent bonds. Bonds involving hydrogen can be quite short; the shortest bond of all, H—H, is only 74 pm.
The covalent radius of an atom is determined by halving the bond distance between two identical atoms. Chlorine is used to disinfect drinking water and wastewater, in bleaches, and in the manufacture of chlorinated organic compounds such as the vinyl chloride used in making the plastic PVC, polyvinyl chloride. Chlorine is also found in hydrogen chloride, a colorless gas with a sharp, irritating smell. Hydrochloric acid is also known as "muriatic acid," and under this name is often sold with swimming-pool supplies.
It is used in the synthesis of organochlorine compounds, the "pickling" of steel and other metals to dissolve scale from their surfaces, and many other uses. Hydrochloric acid is also produced in the stomach, where it serves to break down complex foods. Chlorine is found in bleaches and cleaners, usually in the form of sodium hypochlorite, NaOCl, which is also used to kill bacteria in drinking water.
Carbon tetrachloride, CCl 4 , used to be used in dry cleaning and as a spot remover; this substance is now restricted by the Montreal Protocols link because of its effect on the ozone layer. Chloroform, or trihalomethane, is a very commonly used organic solvent; chloroform vapor is a anesthetic: James Young Simpson was the first to use chloroform as an anesthetic during childbirth in presumably, not on himself!
However, since chloroform is carcinogenic, and toxic to the liver, it is not widely used for this purpose anymore. It's also useful for knocking out giant apes. Bromine is a dark, reddish-brown liquid at room temperature the only nonmetallic element that is a liquid at room temperature with a terrible smell. The name "bromine" is derived from the Greek word for "stench," bromos.
It is found in the Earth's crust at a concentration of 0. It is found as bromide ions, Br - , in the ore bromargyrite [silver bromide, AgBr], in seawater, and some natural sea-salt deposits and brines.
Bromine is often incorporated into organic compounds; organobromo compounds are very useful in many organic synthesis reactions. 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. Nor shall the RSC be in any event liable for any damage to your computer equipment or software which may occur on account of your access to or use of the Site, or your downloading of materials, data, text, software, or images from the Site, whether caused by a virus, bug or otherwise.
Jump to main content. Periodic Table. Glossary Allotropes Some elements exist in several different structural forms, called allotropes. Discovery date Discovered by Bernard Courtois Origin of the name The name is derived from the Greek 'iodes' meaning violet. Allotropes I 2. Glossary Group A vertical column in the periodic table.
Fact box. Group 17 Melting point Glossary Image explanation Murray Robertson is the artist behind the images which make up Visual Elements. Appearance The description of the element in its natural form.
Biological role The role of the element in humans, animals and plants. Natural abundance Where the element is most commonly found in nature, and how it is sourced commercially. Uses and properties. Image explanation. The image is of seaweed. Many species of seaweed contain iodine. A black, shiny, crystalline solid. When heated, iodine sublimes to form a purple vapour. Photography was the first commercial use for iodine after Louis Daguerre, in , invented a technique for producing images on a piece of metal.
These images were called daguerreotypes. Today, iodine has many commercial uses. Iodide salts are used in pharmaceuticals and disinfectants, printing inks and dyes, catalysts, animal feed supplements and photographic chemicals. Iodine is also used to make polarising filters for LCD displays. Iodide is added in small amounts to table salt, in order to avoid iodine deficiency affecting the thyroid gland. The radioactive isotope iodine is sometimes used to treat cancerous thyroid glands.
Biological role. Iodine is an essential element for humans, who need a daily intake of about 0. Our bodies contain up to 20 milligrams, mainly in the thyroid gland. This gland helps to regulate growth and body temperature. Normally we get enough iodine from the food we eat. A deficiency of iodine can cause the thyroid gland to swell up known as goitre. Natural abundance. Iodine is found in seawater, as iodide.
It is only present in trace amounts 0. In the past iodine was obtained from seaweed. Now the main sources of iodine are iodate minerals, natural brine deposits left by the evaporation of ancient seas and brackish briny waters from oil and salt wells.
Iodine is obtained commercially by releasing iodine from the iodate obtained from nitrate ores or extracting iodine vapour from the processed brine. Help text not available for this section currently. Elements and Periodic Table History. In the early s, Bernard Courtois of Paris manufactured saltpetre potassium nitrate, KNO 3 and used seaweed ash as his source of potassium. One day in , he added sulfuric acid and saw purple fumes which condensed to form crystals with a metallic lustre.
Courtois guessed this was a new element. In November , they exhibited iodine at the Imperial Institute in Paris. Davy sent a report to the Royal Institution in London where it was mistakenly assumed he was the discoverer, a belief that persisted for more than 50 years. Atomic data. Bond enthalpies. Glossary Common oxidation states The oxidation state of an atom is a measure of the degree of oxidation of an atom.
Oxidation states and isotopes. Glossary Data for this section been provided by the British Geological Survey. Relative supply risk An integrated supply risk index from 1 very low risk to 10 very high risk. Recycling rate The percentage of a commodity which is recycled. Substitutability The availability of suitable substitutes for a given commodity. Reserve distribution The percentage of the world reserves located in the country with the largest reserves. Political stability of top producer A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators.
Political stability of top reserve holder A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators. Supply risk. Relative supply risk 6. Young's modulus A measure of the stiffness of a substance. Shear modulus A measure of how difficult it is to deform a material. Bulk modulus A measure of how difficult it is to compress a substance. Vapour pressure A measure of the propensity of a substance to evaporate.
Pressure and temperature data — advanced. Listen to Iodine Podcast Transcript :. You're listening to Chemistry in its element brought to you by Chemistry World , the magazine of the Royal Society of Chemistry. Hello, this week cretins, fire crackers and clean water.
The story starts in Italy, and here's Andrea Sella. When I was a child, I used spend a couple of weeks each summer high in the Italian Alps in an idyllic little village called Cogne that nestles quietly between high ice-clad peaks. To most Italians the name is associated with a sensational murder. Others know that in winter the valley has some of the finest ice-climbing in the Alps.
But to me, Cogne will always be connected with the element iodine. One afternoon, when I was around 10 years old, returning with my Dad from a long hike, we passed a dull grey building on the edge of the village.
It was surrounded by a tall metal fence and had an institutional look about it. Sitting on the bench all on his own was a strange looking old man - he had rather shaggy hair, a vacant look, and a large, distended pouch of skin where his neck should have been.
I was utterly shocked by this strange being. I pestered my father with questions. Who was he? What was wrong with him? Why did he look so sad? My father, whose patience in the face of a barrage of questions was almost infinite, explained that the poor man had grown up with insufficient iodine in his diet. Iodine, he went on was essential for the proper development of the thyroid gland in the neck, and that if one didn't eat the right kind of salt, especially as a child, one might develop goitre and one's mental development would also be affected.
I would later read of English travellers passing through the Alps referring to The Valleys of the Cretins - travel books of the period often include lurid illustrations of these poor unfortunates. The disease had been known to medical writers for centuries. Galen for example recommended treatment with marine sponges. In Roger of Salerno recommended seaweed.
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