Section 6.4 “Metallic Bonding” Pre-AP Chemistry

Sec 6.4 Vocabulary metallic bonding malleability ductility

Chapter 6 Objectives Section 4 Metallic Bonding 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 compound are not.

Properties of Substances with Metallic, Ionic, and Covalent Bonds Chapter 6 Section 4 Metallic Bonding Properties of Substances with Metallic, Ionic, and Covalent Bonds

Metallic Bonds are… How metal atoms are held together in the solid. Metals hold on to their valence electrons very weakly. Think of them as positive ions (cations) floating in a sea of mobile electrons

Sea of Electrons + Electrons are free to move through the solid. Metals conduct electricity. +

Chapter 6 Section 4 Metallic Bonding 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 (heat) conductivity malleability ductility shiny appearance (luster)

Why metals are Shiny metals are strong absorbers and reflectors of light absorption of light excites metals electrons to higher energy levels electrons immediately fall emitting energy at same frequency as absorbed (reflection of light)

Chapter 6 Section 4 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. Both malleability and ductility explained in terms of the mobility of the valence electrons (sea of electrons)

Due to the mobility of the valence electrons, metals have: Notice that the ionic crystal breaks due to ion repulsion! 1) Ductility 2) Malleability and

Malleable Force +

Malleable Force + Mobile electrons allow atoms to slide by, sort of like ball bearings in oil.

Metallic properties.. The valence electrons of metal atoms can be modeled as a sea of mobile electrons. metals are.. a) good conductors of electric current b) ductile and malleable which explains the mobility of valence e-

Ionic solids are brittle Force + -

Ionic solids are brittle + - Force Strong Repulsion breaks a crystal apart, due to similar ions being next to each other.

Chapter 6 Section 4 Metallic Bonding 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.

Chapter 6 The Metallic-Bond Model, continued Section 4 Metallic Bonding The Metallic-Bond Model, continued The chemical bonding that results from the attraction between metal atoms and the surrounding sea of electrons is called metallic bonding.

Chapter 6 Objectives Section 4 Metallic Bonding 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 compound are not.

End of Sec 6.4