Share This Video. Apne doubts clear karein ab Whatsapp par bhi. Try it now. Ab clear karein apne doubts Whatsapp par bhi. Apna phone number register karein. Ab aap Whatsapp pe solutions paa saktey h, hum aapko message karenge. Ab aap Whatsapp pe solutions paa saktey h, hum aapko ping karenge. Study Materials. Why use Doubtnut? Boron forms compounds with oxygen, hydrogen, the halogens, nitrogen, phosphorus, and carbon only diamond is harder than boron carbide.
It also forms organic compounds. Boron is most commonly used in its compounds, especially borax and boric acid. Boron is used as a deoxidizer and degasifier in metallurgy.
Because it absorbs neutrons, it is used in the shielding material and in some control rods of nuclear reactors. Boron fibers, which have a very high tensile strength, can be added to plastics to make a material that is stronger than steel yet lighter than aluminum. It makes the glass tough and heat resistant. Fibreglass textiles and insulation are made from borosilcate glass.
The isotope boron is good at absorbing neutrons. This means it can be used to regulate nuclear reactors. It also has a role in instruments used to detect neutrons. Biological role.
Boron is essential for the cell walls of plants. We take in about 2 milligrams of boron each day from our food, and about 60 grams in a lifetime. Some boron compounds are being studied as a possible treatment for brain tumours. Natural abundance. Boron occurs as an orthoboric acid in some volcanic spring waters, and as borates in the minerals borax and colemanite. Extensive borax deposits are found in Turkey.
However, by far the most important source of boron is rasorite. High-purity boron is prepared by reducing boron trichloride or tribromide with hydrogen, on electrically heated filaments. Impure, or amorphous, boron can be prepared by heating the trioxide with magnesium powder. Help text not available for this section currently.
Elements and Periodic Table History. It was used as a flux used by goldsmiths. In fact, neither had produced the pure element which is almost impossible to obtain. A purer type of boron was isolated in by Henri Moissan.
Eventually, E. Weintraub in the USA produced totally pure boron by sparking a mixture of boron chloride, BCl 3 vapour, and hydrogen. The material so obtained boron was found to have very different properties to those previously reported. Atomic data.
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 4. 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 Boron Podcast Transcript :. You're listening to Chemistry in its element brought to you by Chemistry World , the magazine of the Royal Society of Chemistry. This week we see the true nature of an element wrongly accused of being boring.
I'm Meera Senthilingam from the Naked Scientists. If I had to choose a person to represent gold, then I guess it might be an ambitious young stockbroker, a bit flashy, and not great at forming relationships.
For helium - an airy-fairy blonde with a bit of a squeaky voice, but with aspirations to join the nobility. And for boron? Well at first glance, during the working week at any rate, a boring, middle-aged accountant, maybe wearing brown corduroys and a tweed jacket. Let's start with the boring bit. Boron is usually isolated as a brown, amorphous solid.
I don't know anyone who thinks the element boron has anything interesting about it. But its unexpected side starts to emerge when you look at some simple compounds of boron. Consider the nitride, for example - just the 2 elements at numbers 5 and 7 in the periodic table, but able to join forces to provide hard diamond or soft graphite-like structures, very similar to those of the 6 th element, carbon. Then there is the trifluoride - remember that acids were first classified as substances that could provide protons, but BF 3 is the archetypal Lewis acid, which doesn't have a proton in sight, yet is able to coordinate with lone pairs, allowing it to catalyse an array of reactions.
It can achieve this chemistry because boron really does have two sides to it - it is set up to form 3 bonds with adjacent atoms, but even in this state, readily forms an extra bond in order to complete the 2 nd main shell of 8 electrons. But the real interest, the 'skydiving', starts when we look at the trihydride of boron. We'll return to this later on, as BH 3 has structural subtleties that will really take us into sexy territory.
But at this stage we'll simply see how boron's schizophrenic side can be used to good effect - add BH 3 to an alkene, then throw in some alkaline hydrogen peroxide, and the oxygen first attaches to the boron, and then gets shuttled onto the adjacent carbon, all driven by this balance between 3- and 4-valent boron. This rather complicated reaction mechanistically is very reliable, and has been used for decades now as a simple way of turning alkenes into alcohols. Building on this idea, lots of clever variants allow one to introduce the alcohol very selectively, including my favourite of the reagent made by reacting borane with cycloocta-1,5-diene; the resulting dialkylborane is incredibly selective at attacking only the least substituted carbon of an alkene, and its often abbreviated schematically to a BH unit hanging down from two arcs, leading to its nickname as the parachute molecule.
So much for skydiving - what about motorbikes. Well this bit is rather like seeing what appears to be a 50cc moped, only to find that it goes from 0-to in 3. Let me explain - the name boron comes from the mineral borax, which is a salt of the a really uninspiring acid called boracic acid. You can buy it from any pharmacist, and it's a mildly acidic antiseptic, and it essentially comprises a boron atom attached to three OH groups.
And here's the surprise - you can fairly easily swap one OH for an aryl group, and you generate an aryl boronic acid capable of coupling to a whole range of aryl halides using palladium catalysis. This was a long sought-after process that many had thought impossible in high yield, until a chemist called Suzuki hence the motorbike connection found that boron could solve the trick.
And lastly to the sexy bit. I said that boron trihydride had a structural subtlety, and that is the fact that it was an 'impossible' molecule back in , in that there was no known bonding that could account for its dimeric structure, or that of some related boron hydrides. And then in one of those 'Just William' sort of stories when a youngster gets the better of his elders, Christopher Longuet-Higgins, then an undergraduate at Cambridge, came up with the solution during a tutorial, publishing the landmark paper with his tutor whilst still only But remember, don't just judge elements by their first appearance - they may have hidden secrets and unexpected talents.
So, split personalities, parachute molecules, and swapping partners - I certainly won't be judging this element on its first appearance. Now, next time we meet an element that also believes in humility. When it comes to use lanthanum best resembles a successful movie bit part player.
Someone who never gets the lead role, but appears in film after film, solidly portraying different characters. Not a particularly expensive material to produce, lanthanum's many roles remain of a supporting kind, playing an essential part but avoiding the limelight.
Join Brian Clegg to find out how the humble lanthanum spreads itself around town in next week's Chemistry in its Element. Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.
There's more information and other episodes of Chemistry in its element on our website at chemistryworld.
0コメント