Section 6.4 “Metallic Bonding”

1. Section 6.4“Metallic Bonding” Pre-AP Chemistry

2. Sec 6.4 Vocabulary • metallic bonding • malleability • ductility

3. Chapter 6 Section4 Metallic Bonding Objectives • Describethe electron-sea model of metallic bonding, and explain why metals are good electrical conductors. • Explainwhy metal surfaces are shiny. • Explainwhy metals are malleable and ductile but ionic-crystalline compound are not.

4. Chapter 6 Section4 Metallic Bonding Properties of Substances with Metallic, Ionic, and Covalent Bonds

5. 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

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

7. Chapter 6 Section4 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)

8. 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)

9. Chapter 6 Section4 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)

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

11. + + + + + + + + + + + + Malleable Force

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

13. 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-

14. + - + - - + - + + - + - - + - + Ionic solids are brittle Force

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

16. Chapter 6 Section4 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 electronsaround the metal atoms, which are packed together in a crystal lattice.

17. Chapter 6 Section4 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.

19. Chapter 6 Section4 Metallic Bonding Objectives • Describethe electron-sea model of metallic bonding, and explain why metals are good electrical conductors. • Explainwhy metal surfaces are shiny. • Explainwhy metals are malleable and ductile but ionic-crystalline compound are not.

20. End of Sec 6.4