1 / 14

Bonding in Metals

Bonding in Metals. OBJECTIVES: Use the theory of metallic bonds to explain the physical properties of metals. Bonding in Metals. OBJECTIVES: Describe the arrangements of atoms in some common metallic crystal structures. Metallic Bonds. How atoms are held together in the solid.

eyal
Download Presentation

Bonding in Metals

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Bonding in Metals • OBJECTIVES: • Use the theory of metallic bonds to explain the physical properties of metals.

  2. Bonding in Metals • OBJECTIVES: • Describe the arrangements of atoms in some common metallic crystal structures.

  3. Metallic Bonds • How 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 electrons:

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

  5. Metals are Malleable • Hammered into shape (bend). • Also ductile - drawn into wires. • Both malleability and ductility explained in terms of the mobility of the valence electrons

  6. + + + + + + + + + + + + Malleable

  7. + + + + + + + + + + + + Malleable • Electrons allow atoms to slide by.

  8. + - + - - + - + + - + - - + - + Ionic solids are brittle

  9. - + - + - + - + + - + - - + - + Ionic solids are brittle • Strong Repulsion breaks crystal apart.

  10. Crystalline structure of metal • If made of one kind of atom, metals are among the simplest crystals • Body-centered cubic: • every atom has 8 neighbors • Na, K, Fe, Cr, W

  11. Crystalline structure of metal 2. Face-centered cubic: • every atom has 12 neighbors • Cu, Ag, Au, Al, Pb 3. Hexagonal close-packed • every atom also has 12 neighbors • different pattern due to hexagonal • Mg, Zn, Cd

  12. Alloys • We use lots of metals every day, but few are pure metals • Alloys - mixtures of 2 or more elements, at least 1 is a metal • made by melting a mixture of the ingredients, then cooling • Brass: an alloy of Cu and Zn • Bronze: Cu and Sn

  13. Why use alloys? • Properties often superior to element • Sterling silver (92.5% Ag, 7.5% Cu) is harder and more durable than pure Ag, but still soft enough to make jewelry and tableware • Steels are very important alloys • corrosion resistant, ductility, hardness, toughness, cost

  14. Why use alloys? • Look up alloys in your text book • Types? a) substitutional alloy- the atoms in the components are about the same size • b) interstitial alloy- the atomic sizes quite different; smaller atoms fit into the spaces between larger • Amalgam- dental use, contains Hg

More Related