Understanding Metallic Bonds
This article explains the theory of metallic bonds, common metallic crystal structures and how atoms are held together in the solid form of metals. Metals have a unique bonding characteristic where they hold valence electrons weakly, making them like positive ions floating in a sea of electrons.
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About Understanding Metallic Bonds
PowerPoint presentation about 'Understanding Metallic Bonds'. This presentation describes the topic on This article explains the theory of metallic bonds, common metallic crystal structures and how atoms are held together in the solid form of metals. Metals have a unique bonding characteristic where they hold valence electrons weakly, making them like positive ions floating in a sea of electrons.. The key topics included in this slideshow are metallic bonds, physical properties, crystal structures, valence electrons, positive ions,. Download this presentation absolutely free.
1. Bonding in Metals l OBJECTIVES: Use the theory of metallic bonds to explain the physical properties of metals.
2. Bonding in Metals l OBJECTIVES: Describe the arrangements of atoms in some common metallic crystal structures.
3. Metallic Bonds l How atoms are held together in the solid. l Metals hold on to their valence electrons very weakly. l Think of them as positive ions (cations) floating in a sea of electrons:
4. Sea of Electrons + + + + + + + + + + + + l Electrons are free to move through the solid. l Metals conduct electricity.
5. Metals are Malleable l Hammered into shape (bend). l Also ductile - drawn into wires. l Both malleability and ductility explained in terms of the mobility of the valence electrons
7. Malleable + + + + + + + + + + + + l Electrons allow atoms to slide by.
8. Ionic solids are brittle + - + - + - + - + - + - + - + -
9. Ionic solids are brittle + - + - + - + - + - + - + - + - l Strong Repulsion breaks crystal apart.
10. Crystalline structure of metal l If made of one kind of atom, metals are among the simplest crystals 1. 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 l We use lots of metals every day, but few are pure metals l Alloys - mixtures of 2 or more elements, at least 1 is a metal l made by melting a mixture of the ingredients, then cooling l Brass: an alloy of Cu and Zn l Bronze: Cu and Sn
13. Why use alloys? l Properties often superior to element l 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 l Steels are very important alloys corrosion resistant, ductility, hardness, toughness, cost
14. Why use alloys? l Look up alloys in your text book l Types? a) substitutional alloy - the atoms in the components are about the same size l b) interstitial alloy - the atomic sizes quite different; smaller atoms fit into the spaces between larger l Amalgam- dental use, contains Hg