Metal generally refers to having special luster (i.evisible lightStrong reflection) and opaque, with ductility and thermal conductivity of a class of substances.The narrow concept of metal is a simple substance composed of metal elements[4]。Pure metals are generally solid (except mercury) at room temperature. Most of them are excellent conductors of electricity and heat, with high density and high melting point.[1]Metal resources on the earth widely exist in the crust and ocean. Except for a few very inactive metals such as gold and silver, which exist in the form of simple substances, the rest exist in the form of compounds.[1]Metal widely exists in nature and is widely used in life. It is a very important and most widely used kind of material in modern industry.
The metal has a goodelectric conductionSex, andmetallic elementThe compounds usually have positive valence electricity, but when the temperature is higherNucleusThe resistance will become larger if the thermal shock is blocked.The connection between metal atoms isMetal bondTherefore, the connection can be reestablished if the position is changed at will, which is also the reason why the metal has good extensibility.
The substances belonging to metals include goldsilver、copper、iron, manganese, zinc, etc.At one atmospheric pressure and 25 ℃, all metals are solid except mercury (liquid).Most of the pure metals are silver white (gray), and only a few are not. For example, gold is yellow red, and copper is purple red.Most of the Chinese characters used to name metals have an "item" next to them.
Generally, the substance with positive temperature resistance coefficient is defined as metal.The metal elements are located at the lower left of the "boron astatine boundary", and there are metal elements in five areas, including area s, area p, area d, and area f,Transitional elementAll metal elements.
In solid metal conductors, there are many movablefree electron。Although these electrons are not bound to any particularatom, but they are bound in the metal lattice;Even in the absence of an external electric field, these electrons will still move randomly because of thermal energy.However, within the conductor, the average net current is zero.Select any section inside the conductor, and the number of electrons moving from one side of the section to the other side in any time interval is equal to the number of electrons moving across the section in the opposite direction.
Atomic structure of metal
Announce
edit
excepttin、antimony、bismuthThe number of outermost electrons of a few metals is greater than or equal to 4, while the number of outermost electrons of most metal atoms is less than 4. The arrangement of peripheral electrons of the main group of metal atoms isnsoneornstwoornstwonp(1-4), the peripheral electron arrangement of transition metal can be expressed as（n-1)d(1-10)ns(1-2)。The atomic radii of the main group metal elements are all larger than those of the same periodNonmetallic element（Noble gasExcept).
Non ferrous metals
Announce
edit
Non ferrous metals
In the narrow sense, non-ferrous metals are also called nonferrous metals, which are all metals except iron, manganese and chromium.Nonferrous metals in the broad sense also include nonferrous alloys.Nonferrous alloy is an alloy formed by adding one or several other elements with a nonferrous metal as the matrix (usually more than 50%).
The strength and hardness of non-ferrous alloys are generally higher than that of pure metals, the resistance is larger than that of pure metals, the resistance temperature coefficient is smaller, and the non-ferrous alloys have good comprehensive mechanical properties.Common nonferrous alloys include aluminum alloy, copper alloy, magnesium alloy, nickel alloy, tin alloy, tantalum alloy, titanium alloy, zinc alloy, molybdenum alloy, zirconium alloy, etc.
Copper in nonferrous metals is one of the earliest metal materials used by human beings.Modern nonferrous metals and their alloys have become indispensable structural and functional materials in machinery manufacturing, construction, electronic industry, aerospace, nuclear energy utilization and other fields.[2]
Synthetic metal
Announce
edit
titanium alloy
A substance with metal characteristics composed of two or more chemical elements, at least one of which is a metal element, is called an alloy.Alloys composed of two elements are collectively referred to as“Binary alloy”The alloy composed of more than three elements is generally called“Multicomponent alloy”。The structure and properties of an alloy depend on the interaction between the components that make up the alloy.
The crystal of the alloy is composed of different kinds of atoms, and has different crystal structures and properties according to the interaction of the constituent elements.Nickel chromium alloyWith high resistivity and heat resistance (1000 ℃~1200 ℃), it is commonly used as electric furnace wire.aluminium alloyThe strength of unit weight is close toHigh quality steel。Beryllium bronzeIt has extremely high hardness and strength, good elasticity, strong corrosion resistance, good weldability and machinability, and is commonly used to manufacture special bearings, elastic elements, and spark free tools.Because the mechanical, physical and chemical properties of alloys are often better than pure metals, almost all metal materials used in industry are alloys.
Common metals: such as iron, aluminum, copper, zinc, etc.
Rare metals: such as zirconium, hafnium, niobium, tantalum, etc.
Light metal: the density of metal is less than 4500kg/mthree, such as titanium, aluminum, magnesium, potassium, sodium, calcium, strontium, barium, etc.
Heavy metal: the density of metal is more than 4500kg/mthree, such as copper, nickel, cobalt, lead, zinc, tin, antimony, bismuth, cadmium, mercury, etc.
Precious metals: they are more expensive than commonly used metals, and the crustal abundance is low (also known as CLARKE value, a value representing the average content of chemical elements in the crust). It is difficult to purify, such as gold, silver and platinum group metals.
Quasi metallic elements: between metals and nonmetals in nature, such as germanium, antimony, polonium, etc.
Rare metals: including rare light metals, such as lithium, rubidium, cesium, etc;Rare and refractory metals: such as zirconium, molybdenum, tungsten, etc;Rare and dispersed metals: such as gallium, indium, germanium, thallium, etc;Rare earth metals: such as scandium, yttrium and lanthanide metals;Radioactive metals: such as radium, francium, polonium and uranium and thorium in actinides.
chemical property
Announce
edit
Metals are divided into active metals and passive metals.According to the order of metal activity, the metal before hydrogen is called active metal, and the metal after hydrogen is passive metal.
Potassium calcium sodium magnesium aluminum zinc iron tin lead (hydrogen) copper mercury silver platinum
K Ca Na Mg Al Zn Fe Sn Pb (H) Cu Hg Ag Pt Au
1. Metal in front of hydrogen can react with weak oxidizing strong acid to replace hydrogen in acid（concentrated sulfuric acid、nitric acidThe strong oxidizing acid with equal strength does not react with metal to generate hydrogen), such as: Fe+2HCltwo+ Htwo↑
2. Metal with strong activity can react with metal salt solution with weak activity.
4. In theory, all metals in front of H can react with water.At room temperature, potassium, calcium, sodium, etc. can react violently with water, magnesium, aluminum, etc. can react with hot water, and iron and other metals can react with water vapor at high temperatures.
5. None of metalOxidizabilityHowever, metal ions are generally oxidizing (such as Fe3+, Cu2+, Ag+）The weaker the activity is, the stronger the ionic oxidation is.
6. All metalsReducibilityThe metal with weaker activity has weaker reducibility.
Some metal applications
Announce
edit
Metal elements are the main body of chemical elements and the main material resources for people's production and life.
Tungsten (W): among various metal elements, tungsten is the most difficult to melt and volatilize.Tungsten is mainly used to make alloy steel;Pure tungsten is mainly used to make tungsten filament in the lamp, and also used in electronic instruments, optical instruments, etc.
Chromium (Cr): Chromium is a silver white metal with high hardness and corrosion resistance. It is used for electroplating and manufacturing special steel.In this century, when people were committed to studying the hard properties of chromium, they inadvertently discovered its corrosion resistance, which led to the birth of stainless steel.Now, stainless steel and chrome plated products have been widely used in medical devices, drinking utensils, tableware and other fields.
Manganese (Mn): pure manganese is hard and brittle, which is difficult to be used in production and life. However, manganese alloys are widely used.Manganese steel is hard and tough. It is an ideal material for making rails, bearings and armor plates.
Lithium: Lithium is the lightest metal element with the largest specific heat.Lithium is not only used to manufacture ultra light alloys and lithium batteries, but also an important material for cutting-edge technology.Lithium alloys can greatly reduce weight and energy consumption in aerospace industry, and play an important role in atomic energy industry;In metallurgical industry, lithium is often used as deoxidizer and degasser to eliminate pores and bubbles in metal castings.
Titanium (Ti): The specific strength (ratio of strength to specific gravity) of titanium is the highest among all metal elements.Titanium and titanium based alloys are new structural materials, hard and light, which are mainly used to manufacture aircraft, submarines, corrosion resistant chemical equipment and various mechanical parts.Titanium alloy can maintain high strength in the temperature range of - 253~500 ° C, and is an ideal aerospace material.In steelmaking, a small amount of titanium is also a good deoxidizer, nitrogen remover and desulfurizer.[3]
The most metal
Announce
edit
The metal element with the highest content in the crust: aluminum (7.73%)
The highest content of metal element in human body: calcium (1.5%)
At present, the world's highest annual output of metal: iron
The metal with the smallest density: hydrogen (in January 2016, British scientists first made metallic hydrogen at Edinburgh University, and hydrogen became the metal with the smallest density)
Metal with the highest density: osmium (22.48 × 10 ³ kg/m ³)
Hardest metal: chromium (Mohs hardness is about 9)
Softest metal: cesium (Mohs hardness is about 0.5)
The most conductive metal: silver
The most conductive metal: silver
The most important metal for manufacturing new high-speed aircraft: titanium (called "the metal of the 21st century" or "the steel of the future" by scientists)
Radioactive element with the largest reserves in seawater: uranium (the total reserves of terrestrial uranium mines are about 2 million tons, and the total amount of uranium in the ocean is up to 400000 tons)
The element with the most isotopes: tin (there are 10 stable isotopes)
The element with the least isotope: sodium (only Na-23 is stable)
The most malleable metal: gold (the thinnest gold is only 1/10000mm thick)
The metal with the best ductility: platinum (the diameter of the smallest platinum wire is only 1/5000mm)
Metal with the highest melting point: tungsten (melting point: 3410 ℃)
Metal with the lowest melting point: mercury (melting point: - 38.8 ℃)
The element with the largest difference in melting and boiling points is gallium (melting point 30 ℃, boiling point 2403 ℃)
Francium is the least abundant metal in the crust (even among the most abundant ores, only 37 × 10 per ton-13g；The content in the crust is about 1 × 10-21%）
The metal element that is most likely to generate current under light: cesium (when its surface is irradiated by light, electrons can obtain energy to escape from the surface and generate photoelectric current)
The most metallic metal: cesium
The most expensive metal in the world: californium (US $10 million per gram, more than 500000 times more expensive than gold)
The cheapest metal in the world: iron
The most applicable superconducting element: niobium (when cooled to - 263.9 ℃, it will become a superconductor with almost no resistance)
Metal element that can absorb gas most: palladium (1 volume of colloidal palladium can absorb 1200 volumes of hydrogen)
