They are materials that are obtained by heating minerals in a furnace, generally oxides and sulfides of the metal, obtained in the mines.
Common properties of metals¶
Although different metals have very different properties, there are some properties common to all of them.
- Mechanical resistance of metals
- The mechanical resistance of most metals is very good. Better than any other material. This is the reason why they are used to make structures. For example buildings, planes, cars, ships, etc.
- Malleability and Ductility
- Most metals are very malleable and very ductile, making them much easier to make into thin sheets and wires.
- Metal density
It is highly variable, but in general they are much denser than water.
Metal Density (kg/litre) Magnesium 1.7 Aluminum 2.7 Titanium 4.5 Iron 7.9 Copper 9.0 Lead 11.3 Mercury 13.5 Gold 19.3
- Conductivity of metals
- They are good conductors of heat and electricity.
There are metals, such as iron, that oxidize non-stop until the corrosion completely destroys them.
Some metals such as aluminum, silver or lead oxidize on the surface and lose their metallic shine. This surface oxide layer protects them by preventing oxidation from progressing. Thus, these metals are resistant to corrosion.
Other metals such as gold, platinum or chrome maintain their metallic shine without oxidizing on the surface.
- Response to light
- Metals are opaque and, polished, they reflect light well. They have a characteristic shine called "metallic".
- Ecological properties of metals
Metals are easily recyclable many times without degrading.
Many metals are inert and do not react with nature, oxidizing very slowly without producing toxins.
Heavy metals are very toxic to the environment.
- Other properties of metals
- There are metals that are liquid at room temperature (mercury and gallium) that can be used to make thermometers, fluorescent tubes, etc.
Periodic table of elements¶
Metals make up the majority of the elements represented on the periodic table.
An alloy is a mixture of a metal with another element. Alloys are generally made by melting a metal with other elements so that they combine so that the result has the properties of both.
Examples of alloys are bronze, brass, steel or cast iron.
Most metals are not used in their pure form, but instead are alloyed with other elements to improve their properties.
- Ferrous metals: composed mainly of iron. They are the most used because of their low price.
- Copper and its alloys: Copper, bronze and brass. They are highly appreciated for their good conductivity, their mechanical resistance (bronze) and resistance to corrosion.
- Light metals: mainly aluminum, titanium, magnesium and their alloys. They are very useful for manufacturing airplanes, prostheses, mobiles, light bicycles, etc.
- Heavy metals: lead, mercury, arsenic, cadmium, chromium, nickel, tin, zinc. They are very toxic to the environment.
- Noble metals: are metals with great resistance to corrosion, which do not rust. Gold, silver, platinum, rhodium, iridium, osmium.
- Rare Earth Metals: Neodymium, Yttrium, Lanthanum, Cerium Used to form alloys, electronics, high-performance magnets, and superconductors.
They are those that are formed mainly by iron. Pure iron is a metal with poor mechanical properties, which is why these are usually improved by means of alloys.
Its density is relatively high (7.8 kg/litre).
- It is an alloy of iron with carbon (with a percentage less than 2.1% by weight). It is one of the most widely used metal alloys for all types of products and structures because it is the cheapest metal, with very good mechanical resistance (breaking load of 50 to 100 kg/mm2) and very tough.
It is an alloy of iron with carbon (with a percentage greater than 2.1% by weight). They are more brittle than steel and have a lower melting point. They are more resistant to corrosion and temperature changes than common steels.
They are used, for example, to make manhole covers, stoves and chimneys, water pump casings, etc.
- Stainless steel
- It is an alloy of iron with chromium (with a percentage greater than 10%). It is highly resistant to corrosion and is used in kitchen utensils, cutlery, sinks, pipes, etc.
It is composed of alpha iron pure, dark-looking. Sometimes it is alloyed with cobalt, nickel, zinc or manganese, which improve its magnetic properties.
Ferrite has magnetic properties, which is why it is used to make transformers, magnets, cable filters, etc.
Copper and its alloys¶
It is a reddish metal that is a very good conductor of heat and electricity.
It is widely used to manufacture cables, pipes, heat exchangers, coins, pigments, etc. It was the first metal used in prehistory, giving its name to the Copper Age.
Copper and tin alloy (with a percentage between 3% and 20%). It is very resistant to rubbing and corrosion.
It is used to build musical instruments, boat propellers, or sculptures.
It was the first alloy obtained by humanity and gives its name to the Bronze Age.
It is an alloy of copper and zinc.
It has a characteristic golden color, similar to gold, which is why it is widely used in decoration and costume jewellery. It is also used to make locks, bolts, handles, faucets, vases, etc.
It is the most widely used metal after steel because it is cheap, has a low density (2.8 kg/litre) and very good resistance to corrosion. In its pure state it is very soft and has low mechanical resistance, but when properly alloyed it greatly increases its mechanical resistance to breakage up to 40 kg/mm2.
It is very ductile and malleable and can be easily extruded.
It is used to make window frames, metallic paper, cans, airplanes, electric cables, etc.
Despite being the most abundant metal in the earth's crust during the 19th century, its production was so expensive that it was considered an exotic material with a huge price, higher than that of gold.
From 1900 its production was increasing without stopping until today. This was due to the invention of chemical techniques (Bayer process) and the application of the dynamo that allows the electricity necessary to isolate aluminum by electrolysis to be produced.
It is a gray metal, with a low density (4.5 kg/litre) that is highly resistant to corrosion and with good mechanical resistance to breakage, up to 140 kg/mm2.
It has the best hardness/density ratio of all metals. It is almost as strong as steels, but with less density.
Thanks to its properties, it is highly appreciated for building medical prostheses, aerospace machinery, transporting chemical products, etc. Titanium oxide is used to make white paints and plastics with a very pure color and very good resistance to solar radiation.
It is a dark gray metal that melts easily (327ºC).
It is used in welding electronic components, car batteries, anti-radiation shields, pigments, bullets, etc.
Currently, its use tends to be reduced because it is highly polluting. For example, electronic products increasingly use silver-based solder and components to avoid the use of lead.
It is a shiny silvery liquid metal at room temperature.
It is trying to reduce its use as much as possible to avoid the consequences of its toxicity.
It is used to make fluorescent lights, thermometers, amalgam for fillings, batteries, etc.
It is a shiny white metal. It is very soft and does not rust.
Tin is steel coated with a thin layer of tin and is used in tin cans. Other uses of tin are soldering electronic components, manufacturing bronze and glass, pigments, overcaps for wine bottles, etc.
It is a soft, shiny white metal.
It is used, alloyed with copper, to produce brass. You can coat iron parts in a process called galvanizing that prevents them from rusting. It is also found in electric batteries.
It is a grayish-white metal that is hard, brittle and highly resistant to corrosion.
It is used alloyed with steel to make stainless steel. Chrome plating consists of depositing a protective layer of chrome on another material (plastic, other metals, etc.) giving a shiny appearance that does not rust. Other applications are paints, leather tanning, catalysts, etc.
It is a white metal with a slight yellow hue.
It is used alloyed with steel to make stainless steel. Copper-nickel alloys are highly resistant to corrosion and are used to manufacture marine engines, the chemical industry, or to mint coins.
It is a bluish-white metal.
It is used in rechargeable Nickel-Cadmium batteries, to make bearings with low friction and high resistance to fatigue.
It is a golden, soft, very ductile metal, very resistant to oxidation and a very good electrical conductor.
Most of the gold (70%) is used in jewelry or as an investment. Only 10% of gold is used in industrial applications.
It is used to cover electrical contacts that do not oxidize, electrical wires of chips, light reflector on crystals, etc.
It is a grayish white metal.
It is used in jewelry, electrical contacts, fillings, and catalysts.
Silvery white metal.
It is used as a catalyst for nitrous oxides in automobiles and has no substitute. For this reason, its price has risen so much that it is currently the most expensive precious metal, with a price much higher than that of gold.
There are several references, but the most prestigious is the London Stock Exchange. These prices correspond to the market closing on the pure metal on July 1, 2021.
 Average price of steel. It can vary from 0.42 to 0.65 €/kg.
Precious metals. Price as of July 1, 2021.
Multiple choice questionnaire on metallic materials.