Like other groups, the members of this family show patterns in electron configuration, especially in the outermost shells, resulting in trends in chemical behavior; however, rhodium deviates from the pattern.
Cobalt compounds have been used for centuries to impart a rich blue color to glass, glazes, and ceramics. Cobalt has been detected in Egyptian sculpture, Persian jewelry from the third millennium BC, in the ruins of Pompeii, destroyed in 79AD, and in China, dating from the Tang dynasty (618–907AD) and the Ming dynasty (1368–1644AD).[5]
Swedish chemist Georg Brandt (1694–1768) is credited with discovering cobalt c. 1735, showing it to be a previously unknown element, distinct from bismuth and other traditional metals. Brandt called it a new "semi-metal".[6][7] He showed that compounds of cobalt metal were the source of the blue color in glass, which previously had been attributed to the bismuth found with cobalt. Cobalt became the first metal to be discovered since the pre-historical period. All other known metals (iron, copper, silver, gold, zinc, mercury, tin, lead and bismuth) had no recorded discoverers.
Rhodium was discovered in 1803 by William Hyde Wollaston,[8] soon after he discovered palladium.[9][10][11] He used crude platinum ore presumably obtained from South America.[12] His procedure dissolved the ore in aqua regia and neutralized the acid with sodium hydroxide (NaOH). He then precipitated the platinum as ammonium chloroplatinate by adding ammonium chloride (NH 4Cl). Most other metals like copper, lead, palladium, and rhodium were precipitated with zinc. Diluted nitric acid dissolved all but palladium and rhodium. Of these, palladium dissolved in aqua regia but rhodium did not,[13] and the rhodium was precipitated by the addition of sodium chloride as Na 3[RhCl 6]·nH 2O. After being washed with ethanol, the rose-red precipitate was reacted with zinc, which displaced the rhodium in the ionic compound and thereby released the rhodium as free metal.[14]
Iridium
Chemists who studied platinum dissolved it in aqua regia (a mixture of hydrochloric and nitric acids) to create soluble salts. They always observed a small amount of a dark, insoluble residue.[15] In 1803, British scientist Smithson Tennant (1761–1815) analyzed the insoluble residue and concluded that it must contain a new metal. Vauquelin treated the powder alternately with alkali and acids[16] and obtained a volatile new oxide, which he believed to be of this new metal—which he named ptene, from the Greek word πτηνόςptēnós, "winged".[17][14] Tennant, who had the advantage of a much greater amount of residue, continued his research and identified the two previously undiscovered elements in the black residue, iridium and osmium.[15][16] He obtained dark red crystals (probably of Na 2[IrCl 6]·nH 2O) by a sequence of reactions with sodium hydroxide and hydrochloric acid.[14] He named iridium after Iris (Ἶρις), the Greek winged goddess of the rainbow and the messenger of the Olympian gods, because many of the salts he obtained were strongly colored.[a][18] Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804.[15][19]
The first three elements are hard silvery-white metals:
Cobalt is a metallic element that can be used to turn glass a deep blue color. Cobalt is primarily used in lithium-ion batteries, and in the manufacture of magnetic, wear-resistant and high-strength alloys. The compounds cobalt silicate and cobalt(II) aluminate (CoAl2O4, cobalt blue) give a distinctive deep blue color to glass, ceramics, inks, paints and varnishes. Cobalt occurs naturally as only one stable isotope, cobalt-59. Cobalt-60 is a commercially important radioisotope, used as a radioactive tracer and for the production of high-energy gamma rays. Cobalt is also used in the petroleum industry as a catalyst when refining crude oil. This is to clean it of its sulfur content, which is very polluting when burned and causes acid rain.
Rhodium can be used in jewelry as a shiny metal. Rhodium is a hard, silvery, durable metal that has a high reflectance. Rhodium metal does not normally form an oxide, even when heated. Oxygen is absorbed from the atmosphere only at the melting point of rhodium but is released on solidification. Rhodium has both a higher melting point and lower density than platinum. It is not attacked by most acids as it is completely insoluble in nitric acid and dissolves slightly in aqua regia.
Iridium is mainly used as a hardening agent for platinum alloys. Iridium is the most corrosion-resistant metal known as it is not attacked by acids, including aqua regia. In the presence of oxygen, it reacts with cyanide salts. Traditional oxidants also react, including the halogens and oxygen at higher temperatures. Iridium also reacts directly with sulfur at atmospheric pressure to yield iridium disulfide.
All known isotopes of meitnerium are radioactive with short half-lives. Only minute quantities have been synthesized in laboratories. It has not been isolated in pure form, and its physical and chemical properties have not been determined yet. [citation needed] Based on what is known, meitnerium is considered a homologue to iridium.
Of the group 9 elements, only cobalt has a biological role. It is a key constituent of cobalamin, also known as vitamin B12, the primary biological reservoir of cobalt as an ultratrace element.[22][23]Bacteria in the stomachs of ruminant animals convert cobalt salts into vitamin B12, a compound which can only be produced by bacteria or archaea. A minimal presence of cobalt in soils therefore markedly improves the health of grazing animals, and an uptake of 0.20mg/kg a day is recommended, because they have no other source of vitamin B12.[24]
Proteins based on cobalamin use corrin to hold the cobalt. Coenzyme B12 features a reactive C-Co bond that participates in the reactions.[25] In humans, B12 has two types of alkylligand: methyl and adenosyl. MeB12 promotes methyl (−CH3) group transfers. The adenosyl version of B12 catalyzes rearrangements in which a hydrogen atom is directly transferred between two adjacent atoms with concomitant exchange of the second substituent, X, which may be a carbon atom with substituents, an oxygen atom of an alcohol, or an amine. Methylmalonyl coenzyme A mutase (MUT) converts MMl-CoA to Su-CoA, an important step in the extraction of energy from proteins and fats.[26]
↑ Georg Brandt first showed cobalt to be a new metal in: G. Brandt (1735) "Dissertatio de semimetallis" (Dissertation on semi-metals), Acta Literaria et Scientiarum Sveciae (Journal of Swedish literature and sciences), vol. 4, pages 1–10. See also: (1) G. Brandt (1746) "Rön och anmärkningar angäende en synnerlig färg—cobolt" (Observations and remarks concerning an extraordinary pigment—cobalt), Kongliga Svenska vetenskapsakademiens handlingar (Transactions of the Royal Swedish Academy of Science), vol. 7, pp. 119–130; (2) G. Brandt (1748) "Cobalti nova species examinata et descripta" (Cobalt, a new element examined and described), Acta Regiae Societatis Scientiarum Upsaliensis (Journal of the Royal Scientific Society of Uppsala), 1st series, vol. 3, pp. 33–41; (3) James L. Marshall and Virginia R. Marshall (Spring 2003) "Rediscovery of the Elements: Riddarhyttan, Sweden". The Hexagon (official journal of the Alpha Chi Sigma fraternity of chemists), vol. 94, no. 1, pages 3–8.
↑ Usselman, Melvyn (1978). "The Wollaston/Chenevix controversy over the elemental nature of palladium: A curious episode in the history of chemistry". Annals of Science. 35 (6): 551–579. doi:10.1080/00033797800200431.
↑ Münzenberg, G.; Armbruster, P.; Heßberger, F. P.; Hofmann, S.; Poppensieker, K.; Reisdorf, W.; Schneider, J. H. R.; Schneider, W. F. W.; Schmidt, K.-H.; Sahm, C.-C.; Vermeulen, D. (1982). "Observation of one correlated α-decay in the reaction 58Fe on 209Bi→267109". Zeitschrift für Physik A. 309 (1): 89. Bibcode:1982ZPhyA.309...89M. doi:10.1007/BF01420157. S2CID120062541.
↑ Yamada, Kazuhiro (2013). "Chapter 9. Cobalt: Its Role in Health and Disease". In Astrid Sigel; Helmut Sigel; Roland K. O. Sigel (eds.). Interrelations between Essential Metal Ions and Human Diseases. Metal Ions in Life Sciences. Vol.13. Springer. pp.295–320. doi:10.1007/978-94-007-7500-8_9. ISBN978-94-007-7499-5. PMID24470095.
↑ Schwarz, F. J.; Kirchgessner, M.; Stangl, G. I. (2000). "Cobalt requirement of beef cattle – feed intake and growth at different levels of cobalt supply". Journal of Animal Physiology and Animal Nutrition. 83 (3): 121–131. doi:10.1046/j.1439-0396.2000.00258.x.
↑ Smith, David M.; Golding, Bernard T.; Radom, Leo (1999). "Understanding the Mechanism of B12-Dependent Methylmalonyl-CoA Mutase: Partial Proton Transfer in Action". Journal of the American Chemical Society. 121 (40): 9388–9399. doi:10.1021/ja991649a.
Cobalt Co Atomic Number: 27 Atomic Weight: 58.933195 Melting Point: 1768.15 K Boiling Point: 3200 K Specific mass: 8.86 g/cm3 Electronegativity: 1.88
Rhodium Rh Atomic Number: 45 Atomic Weight: 102.90550 Melting Point: 2239.15 K Boiling Point: 3968 K Specific mass: 12.41 g/cm3 Electronegativity: 2.28
Iridium Ir Atomic Number: 77 Atomic Weight: 192.217 Melting Point: 2716.15 K Boiling Point: 4701 K Specific mass: 22.56 g/cm3 Electronegativity: 2.2
Meitnerium Mt Atomic Number: 109 Atomic Weight: [278] Melting Point:? K Boiling Point:? K Specific mass:? 37.4 g/cm3 Electronegativity:?
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