The properties of metals are those qualities that are attributed to metals . A metal is a chemical element or an alloy made of the mixture of metals. Among the best known properties are good conductors of heat, sound and electricity at room temperature and at atmospheric pressure.
The word “metal” arises from metallon,with which the Greeks described the mining excavations.
The metals are obtained from minerals extracted from mines, through metallurgical processes. The extraction process involves the reduction of the ions to the elemental metal (with oxidation number equal to zero).
Physical properties of metals
The physical properties of metals refer to those observable and measurable qualities that do not alter the composition of the compound.
It is not correct to say that all metals in general are strong or hard materials with melting points and high densities. For example, antimony, bismuth and manganese are brittle metals, while sodium and potassium are soft metals.
One of the properties that normally distinguish metals is brightness. In fact, one of the brightness ratings is “metallic brightness.” However, compounds with silicon, a non-metal, also exhibit brightness. For example, quartz is a compound of silicon and oxygen (not metals) that are characterized by its brightness.
Solids at room temperature
Metals appear as solids under normal conditions of temperature and pressure. The classic exception is mercury (Hg), which is found in liquid form at room temperature.
Mercury is found in liquid form.
The malleable property of a metal is applied when it can be struck to form a sheet. That is the property that is applied when iron is forged to make utensils and tools.
Ductility is the ability to deform without breaking. This is the property applicable when we bend a copper, aluminum or iron wire.
High melting point
Metals typically have high melting points. For example, tungsten melts at 3410º and aluminum at 660ºC. Exceptions to this are cesium that melts at 29ºC, mercury at -38ºC and gallium at 30ºC.
All metals have the property of high electrical conductivity in all three dimensions. Silver is the best conductor and plutonium is the worst conductor among metals.
Thermal conductivity is the ability to transfer heat. All metals have a high thermal conductivity. However, there are non-metals that have a high thermal conductivity such as diamond, which is a carbon compound.
Density of metals
The density is the ratio of the mass to the volume of the material. It is generally assumed that metals have a high density. For example, the density of silver (Ag) is 10.5 g / ml, that of copper 8.96 g / ml and that of palladium (Pd) 11.9 g / ml at 20 ° C.
There are exceptions to the rule. The metals lithium (Li), sodium (Na) and potassium (K) are less dense than water. Osmium (Os) has the highest density 22.48g / ml at 20 ° C. Tellurium (Te, a non-metal) has a density of 6.25 g / ml that is greater than the density of 18 metals.
The hardness is the resistance to abrasion. In the Mohs hardness scale the diamond is the maximum of 10 and the talc is 1. The metals of great hardness are iron (4), cobalt (5.5), vanadium (7), titanium (9-) 10) and the metals of lower hardness are cesium and rubidium (0.2-0.3).
Chemical properties of metals
The chemical properties of metals are determined by valence electrons and by their electronegativity.
Formation of cations
The ability to yield valence electrons and form cations is one of the properties of metals. For example, alkali metals, such as sodium and potassium, readily yield an electron. The alkaline earth metals, such as magnesium and calcium, yield the two electrons of their last layer of valence
They act as reducing agents
When a metal reacts with a non-metal, the metal generally acts as a reducing agent, while the non-metal is the oxidizing agent. For example:
Sodium sulphide Na 2 S contains Na + cations and sulfur S- 2 anions .
Metals form ionic compounds with non-metal elements. For example in fluorite or calcium fluoride CaF 2 , calcium is metal and fluorine is non-metal.
Types of metals
Of the 118 elements of the periodic table, 91 are metals. We can classify them into four general groups.
They belong to family 1A of the periodic table. In this group we get sodium (Na), potassium (K), lithium (Li), rubidium (Rb), cesium (Cs) and francium (Fr). In its electronic configuration, the last level has an electron. The elements of this family are very reactive.
Alkali metals, such as Rubidium Rb react with water violently, releasing hydrogen.
Alkaline earth metals
Family 2A includes the alkaline earth metals, among which we can mention beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radon (Ra). In its electronic configuration, the last level has two electrons.
In the center of the periodic table we have the transition metals. In these elements the layer d is partially charged. The first transition series includes scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu). ). The second series of transition are lanthanides and the third series are actinides.
The transition metals behave like typical metals, with metallic brightness and high thermal and electrical conductivity. With regard to hardness, iron and tungsten are very strong and hard and are used as building materials. But copper, gold and silver are comparatively softer.
Between the transition metals and the metalloids, the post-transition metals are located. These include gallium (Ga), indium (In), tin (Sn), thallium (Tl), lead (Pb) and bismuth (Bi).
In group 4A is tin (Sn) and lead (Pb). Both elements have 4 electrons in their last valence level. Tin is a soft, silvery metal, used in alloys such as bronze (20% tin and 80% copper), solder (33% tin and 67% lead) and pewter (85% tin, 7% copper, 6% bismuth, and 2% antimony.
Curiosities about metals
Of the metals we can get many curious facts. Let’s see.
What are heavy metals?
The metals known as heavy metals are those metals of the block composed of the metals of groups 3 to 16 that are in periods 4 and above. This can also be established as the transition and post-transition metals.
Abundant metals on earth
Aluminum (Al) and iron (Fe) are the most abundant metals in the earth.
Metals in the human body
The most abundant metal in the human body is calcium (Ca). This element is part of the bones and teeth, and also participates in biological reactions.
Iron is the element that carries oxygen and carbon dioxide in red blood cells.
Mercury is the classic example of a liquid metal. Gallium (Ga) can be solid at room temperature, but it is so soft that we can cut it with a knife. They are used in the production of semiconductors, in lasers and LED bulbs.