Metals: general characteristics of metals and alloys
The first material that I learned to usepeople for their needs are a stone. However, later, when a person became aware of the properties of metals, the stone moved far back. It is these substances and their alloys that have become the most important and the main material in the hands of people. Of these, objects of daily life, tools of labor were manufactured, and premises were built. Therefore, in this article we will consider what are the metals, the general characteristic, properties and application of which are so actual to this day. After all, literally just behind the stone century, followed by a whole galaxy of metal: copper, bronze and iron.
Metals: a general characteristic
What unites all representatives of thesesimple substances? Of course, this is the structure of their crystal lattice, the types of chemical bonds and the features of the electronic structure of the atom. After all, from this and the characteristic physical properties that underlie the use of these materials by man.
First of all, let's consider metals aschemical elements of the periodic system. In it they are located quite freely, occupying 95 cells from the currently known 115. There are several features of their location in the general system:
- Form the main subgroups of Groups I and II, as well as III, starting with aluminum.
- All the subgroups consist only of metals.
- They are located below the conditional diagonal from boron to astatine.
Based on such data, it is easy to see that nonmetals are collected in the upper right part of the system, and the rest of the space belongs to the elements we are considering.
All of them have several features of the electronic structure of the atom:
- The large atomic radius, as a result of which the connection between the outer electron and the nucleus weakens, so that metals can easily be given up, acting as restorers.
- A small number of electrons on the outer energy layer.
- In the group from top to bottom, the metal properties of the elements increase, and in the period from left to right, on the contrary, weaken. So, the strongest nonmetal is fluoride, and the weak one is France.
General characteristics of metals and non-metalsallows us to identify patterns in their structure. So, the crystal lattice of the first is metallic, special. At its nodes are several types of particles:
Inside, a common cloud is accumulated, called electron gas, which explains all the physical properties of these substances. Type of chemical bond in metals of the same name with them.
There are a number of parameters that unite all metals. The general characteristic of their physical properties is as follows.
- Metallic shine. It has all the representatives of this group of substances. At the same time, most reflect light of one wavelength, so it emits a soft white-silver color. But some (gold, copper, many alloys) shine with a yellow tinge.
- Kovkost and plasticity. This parameter is also inherent in metals. The general characteristic of this feature, however, is not entirely accurate, since among the representatives there are very soft, ductile and ductile, and there are fragile enough to be machined. The most malleable and plastic - gold, silver, copper, aluminum and others. Less pliable - tin, lead, manganese and others.
- Electrical and thermal conductivity. It is enjoyed by all representatives without exception. Metals belong to conductors of the first kind.
- High melting and boiling points. On this basis, they are divided into refractory (temperature above 1500 degrees), fusible - below this figure.
- Light and heavy metals, depending on their density. It is the smaller, the smaller the atomic weight of the element. The easiest is lithium, and heavy is osmium.
- Hardness. The record holder for this indicator is chrome, and the softest is cesium, it melts in hands.
The listed parameters are the totalthe characteristic of metals, that is, all that unites them in one large family. However, it should be understood that there are exceptions to any rule. Moreover, there are too many elements of this kind. Therefore, within the family itself, there are also different subdivisions into different groups, which we shall consider below and for which we indicate characteristic features.
From the point of view of the science of chemistry, all metals are reducing agents. And, very strong. The fewer electrons on the outer level and the larger the atomic radius, the stronger the metal is over the specified parameter.
As a result, metals are able to react with:
- with alkalis (amphoteric metals);
- salts of weaker metals.
This is only a general overview of chemical properties. After all, for each group of elements they are strictly individual.
Alkaline earth metals
The general characteristic of alkaline earth metals is as follows:
- They have two electrons on the outer level.
- Form the second group of the main subgroup of the periodic system, with the exception of beryllium.
- Under normal conditions, these are solids that are not cut with a knife.
- The color of simple metals is silvery-gray, in air they are covered with an oxide film.
- Their chemical activity is high, increasing from magnesium to radium.
- In nature are widely distributed, especially calcium. In a simple form, they do not occur due to high activity, but they form many different, important compounds for humans.
- Are of great importance in the biological plan. Calcium and magnesium are important microelements of the human and animal body. Magnesium is also a part of the chlorophyll of plants.
Thus, the alkaline earth metals arecommon elements of the s-family, exhibiting high chemical activity and being strong reducing agents and important participants in biological processes in the body.
The general characterization of alkali metals beginswith their name. It was received for the ability to dissolve in water, forming alkalis - caustic hydroxides. Reactions with water are very turbulent, sometimes with inflammation. In a free form in nature, these substances are not found, because their chemical activity is too high. They react with air, water vapor, non-metals, acids, oxides and salts, that is, practically everything.
This is due to their electronic structure. On the external level there is only one electron, which they easily give. These are the most powerful reductants, which is why it took them quite a long time to obtain them in their pure form. This was first done by Gemfri Davy already in the 18th century by electrolysis of sodium hydroxide. Now all the representatives of this group are extracted by this method.
General characteristics of alkali metalsis also in the fact that they constitute the first group of the main subgroup of the periodic system. All of them are important elements, forming many valuable natural compounds used by man.
General characteristics of metals of d- and f-families
To this group of elements are all those degreethe oxidation of which can vary. This means that, depending on the conditions, the metal can act as both an oxidizing agent and a reducing agent. Such elements have a great ability to react. Among them, a large number of amphoteric substances.
The general name of all these atoms is transitionalelements. They got it for the fact that, according to the manifested properties, they really stand in the middle, between the typical metals of the s-family and the nonmetals of the p-family.
The general characteristic of transition metals implies the designation of similar properties. They are as follows:
- a large number of electrons at the external level;
- large atomic radius;
- several degrees of oxidation (from +3 to +7);
- valence electrons are on the d- or f-sublevel;
- form 4-6 large periods of the system.
As simple substances, the metals of this group are very strong, ductile and malleable, so they are of great industrial importance.
The subgroups of the periodic table
General characteristics of metals of subgroupscompletely coincides with that of transient ones. And it's not surprising, after all, in fact, it's completely the same thing. Just secondary subgroups of the system are formed precisely by representatives of d- and f-families, that is, transition metals. Therefore, we can say that these concepts are synonyms.
The most active and important of them are the first row of 10 representatives from scandium to zinc. All of them are of great industrial importance and are often used by man, especially for smelting.
General characteristics of metals and alloys allowsunderstand where and how to use these substances. Such compounds have undergone great transformations in the last decades, because all new additives are opened and synthesized to improve their quality.
The most famous alloys are:
- cast iron;
- will win;
- nichrome and others.
What is an alloy? This is a mixture of metals, obtained by melting the latter in special furnace devices. This is done in order to obtain a product that is superior in properties to the pure substances that make up it.
Comparison of the properties of metals and non-metals
If we talk about general properties, thenthe characteristics of metals and nonmetals will differ by one very significant point: for the latter one can not distinguish similar features, since they vary greatly in the properties that are manifested, both physical and chemical.
Therefore, it is impossible to create a similar characteristic for nonmetals. You can only individually consider the representatives of each group and describe their properties.