Metallic Bonding Chemistry 7(D) Understanding metallic bonding will make it easier to understand why metals have the properties they do. Metallic Bonding Chemistry 7(D)

Metallic Bonding Lesson Objectives Explain the characteristics of metallic bonding Use metallic bonding theory to explain metallic properties Electrical conductivity Thermal conductivity Ductility Malleability This presentation will teach you the characteristics of metallic bonding and help you understand how those characteristics influence the properties of metals such as electrical and thermal conductivity, ductility, and malleability.

Metallic Bonding Few electrons occupy the highest energy levels of most metals Empty orbitals in a metal’s outer energy levels overlap Overlapping orbitals allow the outer electrons of metals to move freely Delocalized electrons – electrons that don’t belong to a single atom or bond Delocalized electrons move freely within the metal’s network of unoccupied orbitals Few electrons occupy the highest energy levels of most metals. As a result, empty orbitals in a metal’s outer energy levels overlap. Overlapping orbitals allow the outer electrons of metals to move freely. The outer electrons of metals are delocalized. In other words, they don’t belong to a single atom or bond. Instead, delocalized electrons move freely within the metal’s network of unoccupied orbitals.

Metallic Bonding Electron sea model – atoms of a metal are somewhat fixed in position in a crystal lattice, while outer electrons move freely through out the lattice forming a sea of electrons Metallic cations form when outer electrons move freely throughout the lattice Metallic bond – attraction between delocalized electrons and metallic cations The electron sea model describes these characteristics. The model suggests that atoms of a metal are somewhat fixed in position in a crystal lattice, while the outer electrons move freely throughout the lattice forming a sea of electrons. The free movement of outer electrons throughout the lattice, causes cations to form. Metallic bonding is the attraction between delocalized electrons and metallic cations.

Electrical and Thermal Conductivity Mobility of delocalized electrons causes metals to be excellent conductors Delocalized electrons move heat and electric charge through out a metal quickly By Jan Harenburg (own fotography) [CC-BY-3.0] The mobility of delocalized electrons causes metals to be excellent conductors. Delocalized electrons move heat and electric charge throughout a metal quickly. For example, metals are often used in cookware to transport heat from the heat source to the food. Metals are also used in wiring to transport electric charge from one place to another quickly.

Malleability and Ductility Metallic cations and delocalized electrons slide past each other easily Metals can be changed in shape without causing the crystal to break Malleability – ability to be formed into sheets Ductility – ability to be drawn into wire Since the outer electrons in a metal can move freely, metals can be molded into different shapes. Unlike the cations and anions in an ionic crystal, the metallic cations and delocalized electrons in a metallic crystal slide past each other easily. Ionic crystals break when enough force is applied to alter the alignment of the ions in the crystal. Alterations in alignment cause like charged ions to come into contact, producing repulsion that breaks the ionic crystal. In contrast, when force is applied to metallic crystals, delocalized electrons are able to move and act as a buffer between cations. Therefore, metals can be changed in shape without causing the crystal to break. Malleability and ductility describe the ability of a substance to be changed into different shapes without breaking. Malleability is ability to be formed into sheets, while ductility is the ability to be drawn into wire. Metals are both malleable and ductile, making them suitable for a wide range of applications. I, Daniel Schwen [GFDL] By kurtsik (Forjaria.) [CC-BY-SA-3.0]

Metallic Bonding Lesson Objectives Explain the characteristics of metallic bonding Use metallic bonding theory to explain metallic properties Electrical conductivity Thermal conductivity Ductility Malleability This concludes our presentation on metallic bonding. Now that you understand the characteristics of metallic bonds, you can understand why metals exhibit properties such as electrical and thermal conductivity, ductility, and malleability.