1. Bonding in Metals

2. Objectives Be able to model the valence electrons of metal atoms Describe the arrangement of atoms in a metal Explain the importance of alloys

3. Important Vocabulary Metallic bonds Alloys

4. Metals Metals are made up of closely packed cations rather than neutral atoms The valence electrons of metal atoms can be modeled as a sea of electrons Valence electrons move freely between metal atoms

5. Metallic Bond Is a bond formed by the attraction between positively charged metal ions & the electrons around them Attractive forces between nuclei and neighboring atom’s electrons pack the atoms close together, overlapping the energy levels creating the sea-of-electrons model

6. Metallic Properties Metallic properties can be explained by the sea-of electrons model How? They are malleable and ductile Malleable means that they are easily formed Ductile means that they can be drawn into wires

7. Sea-of-Electrons

8. Crystalline Structure of Metals Metals are crystalline Metals that contain just one kind of atom are among the simplest forms of all crystalline solids Metal atoms are arranged in very compact and orderly patterns 3 main arrangements: body-centered cubic, face-centered cubic, and hexagonal close-packed

9. Body-Centered Cubic Structure Every atom (except those on the surface) has eight neighbors Examples: sodium, potassium, iron, chromium, & tungsten

10. Face-Centered Cubic Structure Every atom has 12 neighbors Examples: copper, silver, gold, aluminum, and lead

11. Hexagonal Close-Packed Structure Every atom has 12 neighbors Examples: magnesium, zinc & cadmium

12. Alloys Are mixtures composed of 2 or more elements, in which at least one is a metal Why are alloys important?

13. Sterling Silver Sterling silver is a mixture of 7.5% copper & 92.5% silver It is harder and more durable than pure silver but soft enough to made into jewelry and tableware

14. Bronze Is an alloy generally containing 7 parts of copper to 1 part of tin It is harder than copper and more easily cast Nonferrous (non-iron) alloys such as, bronze, copper- nickel and aluminum alloys are commonly used to make coins

15. Steels Are the most important alloys The principal elements in most steels are iron, carbon, boron, chromium, manganese, molybdenum, nickel, tungsten, and vanadium Steels have a wide range of useful properties such as, corrosion resistance, ductility, hardness, & toughness Steels are interstitial alloys, the smaller atoms can fit into the interstices (spaces) between the larger atoms

16. Steels