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, implements of labor were made from them, premises were built. Therefore, in this article we will consider what metals are, whose general characteristic, properties and application of which are so relevant to this day. Indeed, right after the Stone Age a whole galaxy of metal followed: copper, bronze and iron.
Metals: general characteristic
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, this is where the characteristic physical properties that underlie the use of these materials by humans are.
First of all, we consider metals as chemical elements of the periodic system. They are located in it quite freely, occupying 95 cells out of 115 currently known. There are several features of their location in the general system:
- They form the main subgroups of groups I and II, as well as III, starting with aluminum.
- All side subgroups are made up of metals only.
- They are located below the conditional diagonal from boron to astatine.
Based on such data, it is easy to trace 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 of the external electron and the nucleus weakens, so metals easily give it away, acting as reducing agents.
- A small number of electrons on the outer energy layer.
- In the group from top to bottom, the metal properties of the elements are enhanced, and on the contrary, from the left to the right, they weaken. So, the strongest non-metal is fluorine, and the weakest is France.
The general characteristic of metals and nonmetals makes it possible to reveal patterns in their structure. So, the crystal lattice of the former is metallic, special. In its nodes are several types of particles:
Inside, a common cloud accumulates, called electron gas, which explains all the physical properties of these substances. A type of chemical bond in metals of the same name with them.
Physical properties
There are a number of parameters that combine all metals. Their general characteristic in physical properties looks like this.
- Metallic shine. All representatives of this group of substances have it. In this case, most reflects light of the same wavelength; therefore, it emits a soft white-silver color. But some (gold, copper, many alloys) shine with a yellow tint.
- Durability and ductility. This parameter is also inherent in precisely metals. The general characteristic for this feature, however, is not entirely accurate, since among the representatives there are very soft, malleable and plastic, and there are quite fragile ones that undergo mechanical processing. The most malleable and plastic ones are gold, silver, copper, aluminum and others. Less malleable - tin, lead, manganese and others.
- Electrical and thermal conductivity. All representatives possess it 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 the indicated 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 chrome, and the softest is cesium, it melts in the hands.
These parameters - this is the general characteristic of metals, that is, all that combines 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 also subdivisions into various groups, which we will consider below and for which we indicate characteristic features.
Chemical properties
From the point of view of the science of chemistry, all metals are reducing agents. Moreover, they are very strong. The fewer electrons at the external level and the larger the atomic radius, the stronger the metal in the specified parameter.
As a result of this, metals are able to react with:
- non-metals;
- water
- acids;
- with alkalis (amphoteric metals);
- oxides;
- salts of weaker metals.
This is just a general overview of chemical properties. Indeed, for each group of elements they are purely individual.
Alkaline earth metals
The general characteristics of alkaline earth metals are as follows:
- At the external level, two electrons.
- The second group forms the main subgroup of the periodic system, with the exception of beryllium.
- Under normal conditions, these are solids that cannot be cut with a knife.
- The color of simple metals is silver-gray; they are coated with an oxide film in air.
- Their chemical activity is high, increasing from magnesium to radiation.
- Widespread in nature, especially calcium. They are not found in simple form due to high activity, however, they form many different compounds important for humans.
- They are of great importance in biological terms. Calcium, magnesium - important trace elements of the human body and animals. Magnesium is also a part of chlorophyll plants.
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 got it for its ability to dissolve in water, forming alkalis - caustic hydroxides. Reactions with water are very violent, sometimes with ignition. In a free form in nature, these substances do not occur, since their chemical activity is too high. They react with air, water vapor, non-metals, acids, oxides and salts, that is, with almost everything.
This is due to their electronic structure. At the external level, there is only one electron that they easily give away. These are the most powerful reducing agents, which is why it took quite a long time to get them in their pure form. This was first done by Humphrey Davy in the 18th century by electrolysis of sodium hydroxide. Now all the representatives of this group are mined by this method.
The general characteristic of alkali metals also lies in the fact that they make up the first group, 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 those whose oxidation state 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 enter into reactions. Among them are a large number of amphoteric substances.
The common name for all these atoms is transition elements. They got it for the fact that according to their properties they really stand 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 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, malleable and malleable, therefore, they are of great industrial importance.
Side subgroups of the periodic system
The general characteristic of the metals of the subgroups completely coincides with that of the transition ones. And this is not surprising, because, in fact, it is absolutely the same thing. Itβs 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 are often used by humans, especially for smelting.
Alloys
The general characteristics of metals and alloys make it possible to understand where and how it is possible to use these substances. Such compounds have undergone major transformations over the past decades, as new additives are 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 melting the latter in special furnace devices. This is done in order to obtain a product superior in properties to the pure substances that form it.
Comparison of the properties of metals and nonmetals
If we talk about general properties, 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 the manifested properties, both physical and chemical.
Therefore, for non-metals it is impossible to create such a characteristic. You can only separately consider the representatives of each group and describe their properties.