Classification of Metals

        A metal is a substance that has properties such as luster (i.e., strong reflection of visible light), ductility, ease of conducting electricity, and heat conduction. The above characteristics of metals are related to the presence of free electrons in metal crystals. In nature, most metals exist in the combined state, while a few metals such as gold, platinum, silver, and bismuth exist in the free state. Most metal minerals are oxides and sulfides. Other forms of existence include chlorides, sulfates, carbonates, and silicates. The connection between metals is a metallic bond, so the connection can be re established by changing the position at will, which is also the reason for the good extensibility of metals. Metallic elements usually exhibit only positive valence in compounds.

        Ferrous metal: Usually refers to iron, manganese, chromium, and their alloys (mainly steel).

        "Manganese and chromium are mainly used in the manufacture of alloy steel, and the surface of steel is often covered with a black layer of ferric oxide. Therefore, iron, manganese, chromium, and their alloys are called ferrous metals.". This classification is mainly based on the extremely important position of steel in the national economy.

        Non ferrous metals: Generally refers to metals other than ferrous metals.

        Light metal: the metal with density below 4.5 g · cm-3 is called light metal. For example, sodium, potassium, magnesium, calcium, aluminum, etc. The group Ⅰ A and Ⅱ A in the periodic system are all light metal.

        Heavy metals: Generally, metals with a density above 4.5 g · cm-3 are called heavy metals. For example, copper, zinc, diamond, nickel, tungsten, molybdenum, antimony, bismuth, lead, tin, cadmium, mercury, and other transition elements are mostly heavy metals.

        Precious metals: Precious metals usually refer to gold, silver, and platinum group elements. These metals are less abundant in the earth's crust, difficult to exploit, and more expensive, so they are called precious metals. These metals are relatively stable to oxygen and other reagents, and gold and silver are often used to make ornaments and coins.

        Rare metals: Rare metals generally refer to metals that are less abundant or dispersed in nature. They are difficult to extract from raw materials, and have been prepared and applied late in industry.

        There is no strict boundary between rare metals and ordinary metals. For example, some rare metals have more content in the earth's crust than copper, mercury, cadmium, and other metals. Rare metals are of great significance in modern industry, and they are often grouped into three categories: ferrous metals, non ferrous metals, and rare metals. www.jiashengsz.com