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Metallic Bonding.  Describe the electron-sea model of metallic bonding, and explain why metals are good electrical conductors.  Explain why metal surfaces.

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Presentation on theme: "Metallic Bonding.  Describe the electron-sea model of metallic bonding, and explain why metals are good electrical conductors.  Explain why metal surfaces."— Presentation transcript:

1 Metallic Bonding

2  Describe the electron-sea model of metallic bonding, and explain why metals are good electrical conductors.  Explain why metal surfaces are shiny.  Explain why metals are malleable and ductile but ionic-crystalline compounds are not.

3  Chemical bonding is different in metals than it is in ionic, molecular, or covalent-network compounds.  Difference is reflected in the unique properties of metals.  They are excellent electrical conductors in the solid state.  Property is due to the highly mobile valence electrons of the atoms that make up a metal.  In metals, the valence electrons are shared by all surrounding atoms.

4  Within a metal, the vacant orbitals in the atoms’ outer energy levels overlap.  The overlapping of orbitals allows the outer electrons of the atoms to roam freely through the entire metal.  The electrons are delocalized, which means they do not belong to any one atom but move freely about the metal’s network of empty atomic orbitals.

5  These mobile electrons form a sea of electrons around the metal atoms, which are packed together in a crystal lattice.  Metallic Bonding: The chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons.  Mobile electrons in the metallic bond are responsible for luster, thermal conductivity, and electrical conductivity.

6  The freedom of electrons to move in a network of metal atoms accounts for the high electrical and thermal conductivity characteristic of all metals.  Because they contain many orbitals separated by extremely small energy differences, metals can absorb a wide range of light frequencies.  Absorption results in the excitation of the metal atoms’ electrons to higher energy levels.  The electrons immediately fall back down to lower levels, emitting energy in the form of light.  De-excitation is responsible for their shiny appearance.  The metals basically absorb then re-emit the light.

7  Most metals are also easy to form into desired shapes.  Malleability: the ability of a substance to be hammered or beaten into thin sheets.  Ductility: The ability of a substance to be drawn, pulled, or extruded through a small opening to produce a wire, without breaking.  The malleability and ductility of metals are possible because metallic bonding is the same in all directions throughout the solid.  In other words, the fact that metals are malleable and ionic crystals are brittle is explained in terms of their chemical bonds.

8  Metallic bond strength varies with the nuclear charge of the metal atoms and the number of electrons in the metal’s electron sea.  Both of these factors are reflected in a metal’s heat of vaporization.  When a metal is vaporized, the bonded atoms in the normal (usually solid) state are converted to individual metal atoms in the gaseous state.  The amount of heat needed to vaporize the metal is a measure of the vapor strength of the bonds that hold the metal together.  In general, the strength of the metallic bond increases moving from left to right on any row of the periodic table.


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