Honors Chemistry

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HONORS CHEMISTRYSection 6.4 – Metallic Bonding

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Metallic Bonding

Chemical bonding is different in metals than it is in ionic, molecular, or covalent-network compounds.

The unique characteristics of metallic bonding gives metals their characteristic properties, listed below.

electrical conductivity

thermal conductivity

malleability

ductility

shiny appearance

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Metallic Bonding

Malleability is the ability of a substance to be hammered or beaten into thin sheets.

Ductility is the ability of a substance to be drawn, pulled, or extruded through a small opening to produce a wire.

These properties are due to highly mobile valence electrons.

Valence electrons are mobile as most of the outer shell of metals is vacant – i.e. in s-block metals all p orbitals are vacant.

Some s, the p and d orbitals are vacant and overlapping.

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Properties of Substances with Metallic, Ionic, and Covalent Bonds

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The Metallic-Bond Model

In a metal, the vacant orbitals in the atoms’ outer energy levels overlap.

This overlapping of orbitals allows the outer electrons of the atoms to roam freely throughout the entire metal.

The electrons are delocalized, which means that they do not belong to any one atom but move freely about the metal’s network of empty atomic orbitals.

These mobile electrons form a sea of electrons around the metal atoms, which are packed together in a crystal lattice.

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The Metallic-Bond Model

The chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons is called metallic bonding.

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Metallic Bond Strength Metallic bond strength varies with nuclear

charge (in a period) and the number of electrons (in a group)

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Metallic Bonding

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Properties of Metals: Surface Appearance

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Properties of Metals: Malleability and Ductility

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Properties of Metals: Electrical and Thermal Conductivity

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Alloys If the atoms are about the same size, we

get a substitution alloy. One kind of atom just takes the place of another kind of atom.

If the added atoms are much smaller than the atoms in the network they can fit into the holes between the layers of atoms in the network. When this happens we call it an interstitial alloy.