金(gold)
一种金属化学元素，属过渡元素，化学符号Au，原子序数为79。金是一种致密、有光泽黄色的贵金属。它以相当纯的形式存在於自然界，色泽悦目、耐用、可永久保存、延展性高。数千年来金是精制珠宝饰物和其他装饰品备受青睐的材料。它被用来制作钱币，以对广泛发行的纸币起保证作用，也是可靠的储备资产。金稀少而又广泛地分布於各种火成岩中；自古以来黄金都是从矿石和矿床发现的（参阅cyanide process）。世界的黄金供应一共有三次大变动︰1492年哥伦布来到新大陆；加州和澳大利亚（1850～1875）发现大量黄金（参阅gold rush）；阿拉斯加和育空（参阅Klondike gold rush）及南非1890～1915发现大量黄金。纯金质软，不耐持续加工，通常用金同铜、银或其他金属制成合金以增大硬度。除用来制造钱币和镶嵌珠宝外，金因导电性好，故其最大的工业用途是在电器工业和电子工业上用作接线柱、印刷电路并用於电镀、半导体系统；金膜对红外辐射反射能力强，已用於太空组件和大楼的窗上；长期以来，金一直用於镶牙。牙科用的合金约75%是金，外加10%的银。在珠宝方面，金的含量分为24个等级，即24开，12开金合金含金50%，24开金即纯金。金的化合物的原子价是1或3，多数用来电镀和其他装饰程序；可溶性盐氯金酸钠（NaAuCl4.2H2O）用於治疗类风湿性关节炎。
English version：
gold
Metallic chemical element, one of the transition elements, chemical symbol Au, atomic number 79. It is a dense, lustrous, yellow, malleable precious metal, so durable that it is virtually indestructible, often found uncombined in nature. Jewelry and other decorative objects have been crafted from gold for thousands of years. It has been used for coins, to back paper currencies, and as a reserve asset. Gold is widely distributed in all igneous rocks, usually pure but in low concentrations; its recovery from ores and deposits has been a major preoccupation since ancient times (see cyanide process). The world's gold supply has seen three great leaps, with Christopher Columbus's arrival in the Americas in 1492, with discoveries in California (see gold rush) and Australia (1850-75), and discoveries in Alaska, Yukon (see Klondike), and South Africa (1890-1915). Pure gold is too soft for prolonged handling; it is usually used in alloys with silver, copper, and other metals. In addition to being used in jewelry and as currency, gold is used in electrical contacts and circuits, as a reflective layer in space applications and on building windows, and in filling and replacing teeth. Dental alloys are about 75% gold, 10% silver. In jewelry, its purity is expressed in 24ths, or karats: 24-karat is pure, 12-karat is 50% gold, etc. Its compounds, in which it has valence 1 or 3, are used mainly in plating and other decorative processes; a soluble chloride compound has been used to treat rheumatoid arthritis.