4.4. Chemical Bonds: Metal bond

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Chemical bonding is one of the fundamental concepts of chemistry, describing the force that holds atoms together to form molecules, compounds, and solids. A detailed understanding of chemical bonds is essential for understanding how materials interact with each other and how they can be manipulated to produce new materials with desired properties. In this chapter, we will focus on metallic bonding, which is a type of chemical bonding that occurs between metal atoms.

Metallic bonding is a type of chemical bonding that involves the delocalization of electrons in a network of metallic atoms. In other words, electrons are not associated with a single atom or a pair of atoms, as in covalent or ionic bonds, but with many atoms. This results in a "cloud" of electrons that is free to move throughout the metal, which explains many of the characteristic properties of metals, such as their electrical and thermal conductivity, ductility and malleability.

The delocalized electrons in a metallic bond are often described as a "sea of ​​electrons". This model, known as the electron sea model, was first proposed by Paul Drude in 1900 and later refined by other scientists. According to this model, the metal atoms in a solid are packed together in a regular lattice, and the atoms' valence electrons are free to move throughout the lattice. This is similar to the way water molecules in an ocean are free to move throughout the mass of water, hence the analogy with a "sea of ​​electrons".

Metallic bonds are responsible for some of the most remarkable properties of metals. For example, the electrical conductivity of metals is due to the free movement of electrons through the metallic lattice. When a voltage is applied to a metal, free electrons are attracted to the positive pole and repel the negative pole, resulting in a flow of electric current. Likewise, the thermal conductivity of metals is due to the ability of electrons to transport thermal energy through the metallic lattice.

The ductility and malleability of metals, which is the ability to be shaped into wires or sheets, is also due to the nature of the metallic bond. When a force is applied to a metal, the atoms in the lattice can move and rearrange themselves without breaking the metallic bond. This is because the delocalized electrons can move and adjust to accommodate the new arrangement of atoms. This allows the metal to be deformed without breaking, making it useful for a variety of applications from jewelry making to building and bridge construction.

In summary, metallic bonding is a type of chemical bonding that occurs between atoms of metals. It is characterized by the delocalization of electrons in a lattice of metal atoms, resulting in a "sea of ​​electrons" that is free to move throughout the metal. This explains many of the characteristic properties of metals, including their electrical and thermal conductivity, ductility, and malleability. A detailed understanding of metallic bonding is essential to understanding the properties and applications of metals in science and industry.

Therefore, understanding metallic bonding and its properties is fundamental to the study of chemistry and is a topic that is often covered on the ENEM exam. The concepts and principles discussed in this chapter will help you better understand this important topic and help you prepare more effectively for the test.

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494.5. Chemical Bonds: Polarity of Bonds