Lead is a chemical element with the symbol Pb (from the Latin plumbum) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is silvery with a hint of blue; it tarnishes to a dull gray color when exposed to air. Lead has the highest atomic number of any stable element and three of its isotopes are endpoints of major nuclear decay chains of heavier elements. Lead is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its amphoteric nature; lead and lead oxides react with acids and bases, and it tends to form covalent bonds. Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group. Exceptions are mostly limited to organolead compounds. Like the lighter members of the group, lead tends to bond with itself; it can form chains and polyhedral structures. Since lead is easily extracted from its ores, prehistoric people in the Near East were aware of it. Galena is a principal ore of lead which often bears silver. Interest in silver helped initiate widespread extraction and use of lead in ancient Rome. Lead production declined after the fall of Rome and did not reach comparable levels until the Industrial Revolution. Lead played a crucial role in the development of the printing press, as movable type could be relatively easily cast from lead alloys.[4] In 2014, the annual global production of lead was about ten million tonnes, over half of which was from recycling. Lead's high density, low melting point, ductility and relative inertness to oxidation make it useful. These properties, combined with its relative abundance and low cost, resulted in its extensive use in construction, plumbing, batteries, bullets and shot, weights, solders, pewters, fusible alloys, white paints, leaded gasoline, and radiation shielding.
Elven gymyk yw plobm, po plomm, niver 82 y'n Vosen Beriodek. Y furvell gymyk yw Pb, dhyworth an ger Latin plumbum, pennfenten an ger kernewek ynwedh. Gwenon kreunek (cumulative) yw plobm, kudyn meur y'n termyn eus passyes, mes kontrolys yn tynn yw devnydh plobm lemmyn. Usys o plobm y'n termyn eus passyes dhe velyshe gwin. Awos hemma, traweythyow veu tardh a 'dhrog torr' hag a ledya dhe vernans. Henwys o Devon colic yn Pow Sows y'n 17ves ha 18ves kansvledhen. Leverir yw nebes tus a vri bos posnys gans plobm: Andrew Jackson (1767-1845), seythves Lywydh an Statys Unys ha Ludwig van Beethoven yw dew anedha. Pur dhe les yw plobm avel skoos rag radyoweythresyans yn klavjiow, rag ensampel arhwilellow dewynnyow-X. Tennys o plobm yn-mes balyow nans yw 6,000 bledhen, hag aswonnys o dhe'n Egyptyonyon Koth. I a usya plobm gwynn ha rudh yn liywow hag afinusterow. An Romanas koth a dhisplegya balyow yn Spayn ha Breten Veur. Y'n Osow Kres usys o dhe worheri tohow drehevyansow, avel eglosyow. Galena (PbS) yw an moon moyha posek, kevys dre vras yn Ostrali (19%), an Statys Unys (13%), China (12%) ha Perou (8%). Kemyskys yw an moon gans kok ha kalgh, ha rostys yw yn fog. An askorrans ollvysel yw 6 milvil tonnas an vledhen. Res yw purhe an plobm awosa gans keworra zynk rag removya arghans dhyworto. Usys o plobm avel keworrans dhe betrol y'n termyn eus passyes, mes lemmyn usys yw dhe wul batriow kerri. Defolyans an plobm yn petrol a wre kawsya skians lehes, yn medh nebes godhonydhyon. Alkan medhel gwann disliw loos-arghansek yw plobm. Poos atomek plobm yw 207.2, y boynt teudhi yw 334°C ha'y boynt bryjyon yw 1740°C. Y dhosedh yw 11.4 kg an liter.langbot langbot