The first material that people have learned to use for their needs is 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 main material in the hands of people. Household items, tools of labor were made from them, premises were built. Therefore, in this article we will consider what metals are, the general characteristics, properties and use of which are so relevant to this day. After all, literally immediately after the Stone Age, a whole galaxy of metal ones followed: copper, bronze and iron.
Metals: general characteristics
What unites all representatives of these simple substances? Of course, this is the structure of their crystal lattice, types of chemical bonds and features of the electronic structure of the atom. After all, hence the characteristic physical properties that underlie the use of these materials by humans.
First of all, consider metals as chemical elements of the periodic system. In it, they are located quite freely, occupying 95 cells out of 115 known to date. There are several features of their location in the generalsystem:
- They form the main subgroups of groups I and II, as well as III, starting with aluminum.
- All secondary subgroups consist of metals only.
- They are located below the conditional diagonal from boron to astatine.
Based on such data, it is easy to see that non-metals 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:
- Large atomic radius, as a result of which the bond between the outer electron and the nucleus weakens, so metals easily give it away, acting as reducing agents.
- A small number of electrons in the outer energy layer.
- In the group from top to bottom, the metallic properties of the elements are enhanced, and along the period from left to right, on the contrary, they weaken. So, the strongest non-metal is fluorine, and the weakest is francium.
The general characteristics of metals and non-metals allows us to identify patterns in their structure. Thus, the crystal lattice of the former is metallic, special. Its nodes contain several types of particles at once:
- ions;
- atoms;
- electrons.
A common cloud accumulates inside, called electron gas, which explains all the physical properties of these substances. Type of chemical bond in metals of the same name with them.
Physical properties
There are a number of parameters that unite all metals. General characteristics of their physicalproperties looks like this.
- Metal shine. All representatives of this group of substances have it. At the same time, most of it reflects light of one wavelength, therefore it emits a soft white-silver color. But some (gold, copper, many alloys) have a yellow sheen.
- Malleability and plasticity. This parameter is also inherent in metals. The general characteristic on this basis, however, is not entirely accurate, since among the representatives there are very soft, malleable and ductile, and there are quite fragile ones that are machined. The most malleable and ductile are gold, silver, copper, aluminum and others. Less malleable - tin, lead, manganese and others.
- Electrical and thermal conductivity. It is possessed by all representatives without exception. Metals are conductors of the first kind.
- High melting and boiling points. On this basis, they are divided into refractory (temperature above 1500 degrees), fusible - below the specified figure.
- Light and heavy metals depending on their density. It is the smaller, the smaller the atomic weight of the element. The lightest is lithium, and the heaviest is osmium.
- Hardness. The record holder for this indicator is chromium, and the softest is cesium, it melts in the hands.
The listed parameters - this is the general characteristic of metals, that is, everything that unites them into one large family. However, it should be understood that there are exceptions to every rule. Moreover, there are too many elements of this kind. Therefore, within the family itself,there are divisions into various groups, which we will consider below and for which we will indicate the characteristic features.
Chemical properties
From the point of view of the science of chemistry, all metals are reducing agents. And, very strong. The fewer electrons in the outer level and the larger the atomic radius, the stronger the metal according to the specified parameter.
As a result of this, metals are able to react with:
- non-metals;
- water;
- acids;
- with alkalis (amphoteric metals);
- oxides;
- s alts of weaker metals.
This is just a general overview of chemical properties. After all, for each group of elements they are purely individual.
Alkaline earth metals
The general characteristics of alkaline earth metals are as follows:
- Have two electrons at the outer level.
- Form the second group of the main subgroup of the periodic system, except for beryllium.
- Under normal conditions, these are solids that cannot be cut with a knife.
- The color of simple metals is silver-gray, covered with an oxide film in air.
- Their chemical activity is high, it increases from magnesium to radium.
- Widespread in nature, especially calcium. In a simple form, they are not found due to high activity, but they form many different compounds that are important for humans.
- Biologically important. Calcium and magnesium are important trace elements of the human body andanimals. Magnesium is also part of plant chlorophyll.
Thus, alkaline earth metals are common elements of the s-family, exhibiting high chemical activity and are strong reducing agents and important participants in biological processes in the body.
Alkali metals
The general characteristic of alkali metals begins with their name. They received it for the ability to dissolve in water, forming alkalis - caustic hydroxides. Reactions with water are very violent, sometimes flammable. These substances are not found in free form in nature, since their chemical activity is too high. They react with air, water vapor, non-metals, acids, oxides and s alts, just about everything.
This is due to their electronic structure. At the outer level, there is only one electron, which they easily give away. These are the strongest reducing agents, which is why it took quite a long time to obtain them in their pure form. This was first done by Humphrey Davy already in the 18th century by electrolysis of sodium hydroxide. Now all representatives of this group are mined using this method.
The general characteristic of alkali metals lies in the fact that they constitute the first group of the main subgroup of the periodic system. All of them are important elements that form many valuable natural compounds used by man.
General characteristics of metals of d- and f-families
This group of elements includes all thosewhose oxidation may 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 enter into reactions. Among them, a large number of amphoteric substances.
The common name for all these atoms is transition elements. They received it for the fact that, in terms of their properties, they really stand, as it were, in the middle, between typical metals of the s-family and non-metals of the p-family.
The general characteristic of transition metals implies the designation of their similar properties. They are as follows:
- a large number of electrons in the outer level;
- large atomic radius;
- several oxidation states (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, therefore they are of great industrial importance.
Side subgroups of the periodic system
The general characteristics of the metals of the secondary subgroups completely coincide with those of the transitional ones. And this is not surprising, because, in fact, it is exactly the same thing. It's just that the side subgroups of the system are formed precisely by representatives of the 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 oftenused by man, especially for smelting.
Alloys
The general characteristics of metals and alloys allows us to understand where and how it is possible to use these substances. Such compounds have undergone great transformations in the last decades, because more and more new additives are being discovered and synthesized to improve their quality.
The most famous alloys today are:
- brass;
- duralumin;
- cast iron;
- steel;
- bronze;
- will win;
- nichrome and others.
What is an alloy? This is a mixture of metals obtained by smelting 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 form it.
Comparison of the properties of metals and non-metals
If we talk about general properties, then the characteristics of metals and non-metals will differ in one very significant point: for the latter, similar features cannot be distinguished, since they differ greatly in their physical and chemical properties.
Therefore, it is impossible to create such a characteristic for non-metals. It is only possible to separately consider the representatives of each group and describe their properties.
