1. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Chapter 23 Metals and Metallurgy Chemistry, The Central Science, 11th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten John D. Bookstaver St. Charles Community College Cottleville, MO

2. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Minerals Most metals are found in solid inorganic compounds known as minerals. Minerals are named by common, not chemical, names.

3. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Minerals Most important metals are found in minerals as oxides, sulfides, or carbonates.

4. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Metallurgy The science and technology of extracting metals from their natural sources and preparing them for practical use.

5. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Metallurgy It involves –Mining. –Concentrating ores. –Reducing ores to obtain free metals. –Purifying metals. –Mixing metals to form alloys that have the properties desired.

6. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Pyrometallurgy Pyrometallurgy is the use of high temperature to alter or reduce minerals.

7. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Calcination Calcination is heating an ore to bring about its decomposition and elimination of a volatile product. PbCO 3 (s)  PbO (s) + CO 2 (g) 

8. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Roasting Roasting is a thermal reaction between an ore and the furnace atmosphere (often oxygen). 2 MoS 2 (s) + 7 O 2 (g)  2 MoO 3 (s) + 4 SO 2 (g) HgS (s) + O 2 (g)  Hg (g) + SO 2 (g)

9. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Smelting This is a melting process in which materials formed during reactions separate into two or more layers.

10. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Refining Refining is the treatment of a crude, relatively impure metal to improve its purity and better define its composition.

11. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Reduction of Iron Hematite (Fe 2 O 3 ), magnetite (Fe 3 O 4 ), and other iron oxides are reduced in blast furnaces. Purified iron exits the furnace at the bottom.

12. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Steel Crude molten iron contains many impurities: –Silicon –Manganese –Phosphorus –Sulfur –Carbon

13. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Steel The impurities are oxidized by O 2 (except phosphorus, which reacts with CaO) to compounds easily separated from the molten iron. Purified molten steel is poured into molds.

14. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Hydrometallurgy These are techniques in which metal is extracted from ore via the use of aqueous reactions.

15. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Leaching Leaching is a process in which a metal- containing compound is selectively dissolved. One can use water if the metal-containing compound is water soluble, but more often one must use acid, base, or a salt solution. 4 Au (s) + 8 CN − (aq) + O 2 (g) + 2 H 2 O (l)  4 Au(CN) 2 − (aq) + 4 OH − (aq) 2 Au(CN) 2 − (aq) + Zn (s)  Zn(CN) 4 2− (aq) + 2 Au (s)

16. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Bayer Process This is a method of purifying bauxite (aluminum ore). Al 2 O 3 ∙ H 2 O (s) + 2 H 2 O (l) + 2 OH − (aq)  2 Al(OH) 4 − (aq) The soluble aluminate ion is separated from the insoluble impurities (SiO 2 and Fe 3 O 3 ) by filtration.

17. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Electrometallurgy The reduction of metal ores or refining of metals by use of electricity is called electrometallurgy.

18. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Sodium NaCl is electrolyzed in a Downs cell. –Gaseous Cl 2 is allowed to disperse. –Molten Na is siphoned off.

19. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Aluminum In the Hall process, Al 2 O 3 is dissolved in molten cryolite (Na 2 AlF 6 ), and Al 3+ is reduced to molten Al.

20. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Copper Active metal impurities are oxidized at the anode, but don’t plate out at the cathode. –Cu 2+ is more easily reduced. Less active metals deposit as sludge below the anode.

21. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Physical Properties of Metals Metals –Conduct heat and electricity. –Are malleable (can be pressed or hammered into sheets). –Are ductile (can be drawn into wire). –Are packed so atoms can slip past each other. So metals aren’t as brittle as other solids.

22. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Electron-Sea Model Metals can be thought of as cations suspended in “sea” of valence electrons. Attractions hold electrons near cations, but not so tightly as to impede their flow.

23. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Electron-Sea Model This explains many of the properties of metals, like –Conductivity of heat and electricity; –Deformation.

24. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Molecular Orbital Model The electron-sea model does not explain observed trends in melting point, boiling point, heat of fusion, etc. –The model suggests these properties should increase with increasing number of valence electrons.

25. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Molecular Orbital Model These trends can be explained by energy bands created by large number of molecular orbitals formed as metal atoms bond with each other.

26. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Molecular Orbital Model As with nonmetals, bond order apexes in center of row, then decreases. Thus, attractions (and melting point, etc.) apex in center of transition metals. (Group 6B)

27. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Alloys Alloys are mixtures of elements that have properties characteristic of metals. Many of the ordinary uses of metals involve alloys.

28. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Solution Alloys Components of alloys are dispersed uniformly— –In substitutional alloys, solute particles take the place of solvent metal atoms. –The particles in these alloys are quite close in size.

29. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Solution Alloys Components of alloys are dispersed uniformly. –In interstitial alloys, solute particles find their way into the holes between solvent metal atoms. –In this type of alloy the solute particles are smaller than the solvent particles.

30. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Intermetallic Compounds Intermetallic compounds are homogeneous alloys with definite properties and compositions. An example is Co 5 Sm, –which is used for permanent magnets in headsets and speakers.

31. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Transition Metals Many important metals are included in this group. The transition metals are the elements in the d block of the periodic table.

32. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Physical Properties of Transition Metals Some of their properties (such as ionization energy, atomic radius, etc.) are suggestive of isolated atoms. Others (such as density, melting point, etc.) suggest bulk solid metal.

33. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Atomic Radii Trends in atomic radii are similar across all three rows of transition metals. While Z eff increases across a row, so does the number of nonbonding electrons. –These repel each other and increase the radius.

34. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Electron Configurations and Oxidation States Transition metals often have more than one common oxidation state. –Most have +2 state due to loss of s electrons. –Oxidation numbers greater than 2 are due to the loss of d electrons as well as s.

35. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Electron Configurations and Oxidation States Many form compounds that have colors.

36. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Electron Configurations and Oxidation States Many have significant magnetic properties. –In diamagnetic elements, all electron spins are paired. –Therefore, there is no net magnetic moment.

37. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Electron Configurations and Oxidation States In paramagnetic atoms and ions, there are unpaired spins. The magnetic fields are randomly arranged, though, unless placed in an external magnetic field.

38. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Electron Configurations and Oxidation States In ferromagnetic substances the orientations of magnetic fields from unpaired electrons are affected by spins from electrons around them.

39. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Electron Configurations and Oxidation States When an external field is applied and then removed, the substance maintains the magnetic moment and becomes a permanent magnet.

40. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Chromium Chromium is oxidized by HCl or H 2 SO 4 to form blue Cr 2+ ion. Cr 2+ is oxidized by O 2 in air to form green Cr 3+. Cr is also found in the +6 state as in CrO 4 2− and the strong oxidizer Cr 2 O 7 2−.

41. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Iron Iron exists in solution in +2 or +3 state. Elemental iron reacts with non-oxidizing acids to form Fe 2+, which oxidizes in air to Fe 3+.

42. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Iron Brown water running from a faucet is caused by insoluble Fe 2 O3. Fe 3+ is soluble in acidic solution, but forms a hydrated oxide as a red- brown gel in basic solution.

43. Metals and Metallurgy © 2009, Prentice-Hall, Inc. Copper In solution copper exists in the +1 or the +2 state. +1 salts are generally white and insoluble. +2 salts are commonly blue and water-soluble.