사용자:Js091213/납
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납(영어: lead 레드[*]) 또는 연(鉛)은 화학 원소로, 기호는 Pb(←라틴어: plumbum 플룸붐[*])이고 원자 번호는 82이다. 이 금속은 다른 금속보다 더 밀도가 높고 무거운 중금속 원소다. 납은 무르고 가단성이 있으며 녹는점이 비교적 낮은 금속이다. 금방 자른 납은 푸른 빛을 띄는 흰색 금속이지만, 공기에 노출 시 어두운 회색 금속으로 변색된다. 납은 안정 원소 중 가장 높은 번호를 가지고 있으며, 납보다 더 큰 원소가 3가지 형태로 붕괴하고 마지막으로 납의 동위 원소로 변하여 안정해진다.
납은 비교적 반응성이 낮은 전이후 금속이다. 납의 약한 금속적 특징은 납의 양쪽성으로 인해 나타난다. 이는 납 산화물이 분자 간 공유 결합을 하는 경향이 있기 때문이다. 납의 화합물은 일반적인 탄소족과 달리 +4보다 +2의 산화수를 가진 상태로 발견된다. Exceptions are mostly limited to organolead compounds. Like the lighter members of the group, lead tends to bond with itself; it can form chains, rings and polyhedral structures.
Lead is easily extracted from its ores; prehistoric people in Western Asia knew of it. Galena, a principal ore of lead, often bears silver, interest in which 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. In 2014, 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 itqjsduranfcnrks extensive use in construction, plumbing, batteries, bullets and shot, weights, solders, pewters, fusible alloys, white paints, leaded gasoline, and radiation shielding.
In the late 19th century, lead's toxicity was recognized, and its use has since been phased out of many applications. Lead is a neurotoxin that accumulates in soft tissues and bones, damages the nervous system, and causes blood disorders. It is particularly problematic in children: even if blood levels are promptly normalized with treatment, permanent brain damage may result.