When an atom is isolated, each electron experiences only the influence of your core and of the rest. But when two particles come together and unite, the electrons corresponding to each atom are subject to the influence of the nucleus and the electrons of the other. The force between these atoms is called a chemical bond.
There are three types: ionic, covalent and metallic. The ionic bond is the product of the attraction between ions of opposite charges, formed with the transfer of electrons. When two atoms that have a covalent bond come together, they generate a different charge, giving rise to a polar type union. Covalent occurs when two atoms share two or more pairs of electrons. The metallic material arises from the electrostatic affinity that is generated in a set of metallic ions and free electrons. Of the latter, the most outstanding aspects will be presented below.
Concept and meaning of metallic bonds in chemistry
Chemical bonds are a type of union that takes place between metallic elements. Where there is no exchange of electrons for the combination. For example, you have a piece of Sodium (Na) whose ions (atom or molecule with a positive or negative charge) are fixed in the metal. Valence electrons move in electron clouds.
There are two theories that support the behavior of these links, which are: the electronic cloud and the bands. As for the first, it was the product of the work of the German physicist Paul Drude, in 1902, and of the physicist Hendrik Lorentz in 1923. They presented a model called “electronic cloud, sea of electrons or electronic or electronic gas”. It states that when the metal binds and the orbitals fuse from the outer shell, obtain similar energy levels in all atoms.
electrons are released from a specific atom, which facilitates their mobility within the reunited orbitals, forming an area expanded by the metallic element. Therefore, the relocated electrons are found generating a delocalization cloud.
For his part, it is said that in 1928 the German physicist Arnold Sommerfield proposed a postulate. Electrons in metallic elements in their quantum arrangement the electrons are almost full at low energy levels. This same year, the Swiss Félix Bloch and some time later the French Louis Brillouin. They applied the postulate to establish the called “band theory” which explains the union of metallic elements.
He suggests that the metal atoms, being so close together, orbitals stack originating bands of energy levels. In this process, two bands are created, the one in which the filled orbitals are found, which have the same amount of energy, is called the valence band. The one of the free orbitals receives the name of conduction band, those who acquire greater energy.
This theory explains the high ability of metals to conduct electricity. Due to the inequality of energy between the bands, it will indicate if it is a semiconducting material, a conductor or an insulator. Also, there are factors that influence the strength of the metallic bond. These are first of all the charge of the ion, since a chemical element with a higher charge will be attracted due to the density of the sea of \u200b\u200bnegatively charged electrons with a lower one.
For example, in the case of the bond formed by aluminum it is stronger than that of magnesium. Well, this loses three electrons, which represents that it transmits this amount of moles for the interaction. On the contrary, Magnesium only gives up two electrons, therefore, it is weaker in relation to aluminum.
Second, the size of the ion. The larger the positive atomic nucleus, the greater the distance of the delocalized electrons. Whereby, decreases electrostatic attraction. As an example we have magnesium (Mg) and calcium (Ca), both have the same charge. Even so, calcium has large ions, which results in weak bonds.
On the other hand, it is essential to identify that alloys are a material that contains the mixture of two or more metals, in a homogeneous way, completely changing the properties of the elements that make it up Such is the case with steel and brass. Used in the construction of railways, bridges, buses, chairs and kitchen utensils.
What are the properties of metallic bonds?
The properties resulting from metallic bonds are:
- Except for mercury (Hg), which is capable of creating shiny and spherical drops, most are solid at room temperature. This is due to the hexagonal or cubic structure of its atoms. Forming crystals.
- present different melting and boiling points.
- are links Very strong.
- They have a metallic luster, that is, reflect incident light on its surface.
- They are ductile originating wires because they can be easily stretched without breaking forming threads.
- excellent conductors of electricity and heat, due to the free movement of electrons.
- the melts They are soluble and in water they are insoluble.
- Are able to reorganize.
- A compound attached through this bond is malleable, that is, it can be reduced to a small sheet, without breaking. Such is the case of silver (Ag) and gold (Au).
What are the characteristics of metallic bonds?
Here we list you the salient characteristics of these links:
- Has greater metallic strength, result of the charges of the cations.
- for being good conductors of thermal energy, They maintain a high amount of kinetics, moving to cold areas.
- With the collision of cations they can dissipate energy or energy is lost.
- They have electrostatic attraction, which spreads all over the metal forming a giant network. They are non-directional.
- present high densities.
How are metallic bonds formed?
It is formed by combining metallic elements. It is known that these require giving up electrons that allow them to achieve the noble gas configuration. Therefore, form an electron cloud losing their valences in the positive nuclei. In this type of bonds, the atoms are divided into twelve, of which six are in an equivalent dimension. Three others are below and three above.
What are the applications of metallic bonds?
Due to their characteristics, metallic bonds have multiple applications. In the case of steel, this is made up of iron and carbon with high tensile strength and used in the manufacture of kitchens, nails, train tracks and bridges. By having in its composition also from iron and carbon, it joins chromium and nickel. Forming stainless steel that serves in obtaining cutlery, pots. Thus in parts for the automotive industry, which are coated to prevent corrosion.
In jewelry, the metallic links formed by gold are used to make chains, earrings, rings, among others, since this it becomes a compact compound. Likewise, it happens with silver and copper. On the other hand, bronze originates from the mixture of copper with tin in an alloy. They are used to make statues and bells.
In the area of health, they are applied to the bonds formed by mercury joined to other elements such as zinc (Zn), tin (Sn), gold (Au), silver (Ag) and copper (Cu) in the production of amalgam. This is used by dentists in restoration of dental pieces that have been damaged by cavities. The unions with copper (Cu) allow the realization of electrical cables. Other applications is the brass that is used in the hardware store for the manufacture of tools. Hearing aids and razor blades have these types of links.
What is the importance of metallic bonds?
These links are important because they allow determining the characteristics and physical properties of metallic elements. The arrangement of electrons in this type of bonds it helps to identify the hardness, ductility, malleability, strength, brightness of the elements. Through them, compact, resistant and solid structures are elaborated because the atoms come together to such an extent that they distribute the valence electrons.
Examples of metallic bonds in chemistry
Metals, being a large group, are frequent and there are many possibilities of generate these links with the pure elements. Therefore, we have as main examples those formed by:
- Silver(Ag).
- Cadmium(Cd).
- Gold (Au).
- Titanium (Ti).
- Lead (Pb).
- Gallium (Ga).
- Platinum (Pt).
- Copper (Cu).
- Nickel (Ni).
- Iron (Fe).
- Zinc (Zn).
- Aluminum (Al).
- Cobalt (Co).
- Palladium (PD).
As a conclusion, all the elements show characteristics that allow them to be differentiated and when united they form different compounds. This coupling is done through a chemical bond according to electron transfer and conditions. Such is the case of the links where metals play a fundamental role and from them their properties change that allow the elaboration of another compound, used in daily life.
