什麼是鐵

金屬化學元素，爲過渡元素的一種，化學符號Fe，原子序數26。鐵是最常使用和最便宜的金屬，在地殼中，其丰度在金屬中居第二位，在所有元素中排在第四位。地殼中游離鐵很少見，而通常存在於合金（特別是隕石）及數百種礦物中，包括赤鐵礦、磁鐵礦、褐鐵礦和菱鐵礦。人體平均含鐵約4.5克，大部分存在於血紅蛋白和它的前身中。鐵在飲食中對健康至爲重要。鐵在常溫下具有鐵磁性，也是唯一可被回火的金屬。其用途廣泛，用於打造各式各樣的鋼，以及用於鑄鐵和熟鐵（統稱「含鐵金屬」）中。用雜質（尤其是碳）來改變其性質是制鋼的基礎。化合物中鐵的原子價爲2（亞鐵）或3（三價鐵）。氧化亞鐵和三氧化二鐵用於製作顏料，後者還用作寶石匠的紅鐵粉。鐵鏽是三氧化二鐵含水分而形成的；鐵氧體是從一種中間的氧化物製得，廣泛用於製造電腦記憶體和磁帶。硫酸亞鐵和硫酸高鐵，以及氯化亞鐵和氯化高鐵在工業應用上均十分重要，如用作媒染劑、還原劑、絮凝劑或原料，還可用於製造墨水、肥料。

iron

Metallic chemical element, one of the transition elements, chemical symbol Fe, atomic number 26. Iron is the most used and cheapest metal, the second most abundant metal and fourth most abundant element in the earth's crust. It occurs rarely as the free metal, occasionally in alloys (especially in meteorites), and in hundreds of minerals and ores, including hematite, magnetite, limonite, and siderite. The human body contains 4.5 g of iron, mostly as hemoglobin and its precursors; iron in the diet is essential to health. Iron is ferromagnetic at ordinary temperatures and the only metal that can be tempered (see tempering). Its uses in steels of various types, as well as in cast and wrought iron (collectively, “ferrous metals”), are numerous. Alteration of its properties by impurities, especially carbon, is the basis of steelmaking. Iron in compounds usually has valence 2 (ferrous) or 3 (ferric). Ferrous and ferric oxides are used as pigments and the latter as jewelers' rouge. Rust is ferric oxide containing water; ferrites, made from an intermediate oxide, are widely used in computer memories and magnetic tapes. Ferrous and ferric sulfates and chlorides are all of industrial importance, as mordants, reducing agents, flocculating agents, or raw materials and in inks and fertilizers.