Ch22

Chapter 22: Main-Group Elements I: Metals: 

Philip Dutton University of Windsor, Canada N9B 3P4 Prentice-Hall © 2002 General Chemistry Principles and Modern Applications Petrucci • Harwood • Herring 8th Edition Chapter 22: Main-Group Elements I: Metals

Contents: 

Contents 22-1 Group 1: the Alkali Metals 22-2 Group 2: The Alkaline Earth Metals 22-3 Ions in Natural Waters: Hard Water 22-4 Group 13 Metals: Aluminum, Gallium, Indium and Thallium 22-5 Group 14 Metals: Tin and Lead Focus On Gallium Arsenide

Group 1: The Alkali Metals: 

Group 1: The Alkali Metals Spodumene LiAl(SiO3)2

The Alkali Metals: 

The Alkali Metals Discoveries are recent. Sodium and potassium (1807) by electrolysis. Cesium (1860) and rubidium (1861) from emission spectra. Francium (1939) from actinium radioactive decay. Most salts are water soluble. Natural brines are good sources. Natural deposits allow mining of solids.

Flame Colors: 

Flame Colors Na K

Table 22.2 Some Properties of the Group 1 (Alkali) Metals: 

Table 22.2 Some Properties of the Group 1 (Alkali) Metals

Production and Use: 

Production and Use 2 NaCl(l) → 2 Na(l) + Cl2(g) Electrolysis: KCl(l) + Na(l) → 2 NaCl(l) + K(g) Sodium as a reducing agent: TiCl4 + 4 Na → Ti + 4 NaCl

Uses of Alkali Metals: 

Uses of Alkali Metals Lithium Alloys of Li-Al-Mg for aircraft and space applications. Battery anodes. Sodium Heat-transfer medium in nuclear reactors. Sodium vapor lamps.

Group I Compounds: 

Group I Compounds Halides NaCl 50 million tons/year in U.S. Preservative, used on roads, water softener regeneration, feed stock for other chemicals KCl from natural brines. Plant fertilizers, feed stock.

Sodium Compounds: 

Sodium Compounds

Carbonates: 

Carbonates Li2CO3 is unstable relative to the oxide. Used to treat manic depression (1-2 g/day). Na2CO3 primarily used to manufacture glass. Currently mined from rich U.S. resources but can be manufactured by the Solvay process.

Diagonal Relationships: 

Diagonal Relationships

Solvay Process: 

Solvay Process

Sodium Sulfate: 

Sodium Sulfate H2SO4(conc. aq) + NaCl(s) → NaHSO4(s) + HCl(g) NaHSO4(s) + NaCl(s) → Na2SO4(s) + HCl(g) In the Kraft Process for making paper: Na2SO4(s) + 4 C(s) → Na2S(s) + 4 CO(g) 100 lb/ton paper

Oxides and Hydroxides: 

Oxides and Hydroxides Reaction with oxygen produces several ionic oxides. In limited oxygen supplies: M2O (small amounts of Li2O2 from Li). In excess oxygen: Li and Na form the peroxide, M2O2. K, Rb and Cs form the superoxide MO2.

Detergents and Soaps: 

Detergents and Soaps

22-2 Group 2: The Alkaline Earth Metals: 

22-2 Group 2: The Alkaline Earth Metals Emerald is based on the mineral beryl: 3BeO·Al2O3 ·6SiO2

Group 2: 

Group 2 Principle forms: carbonates, sulfates and silicates Oxides and hydroxides only sparingly soluble. Basic or “alkaline” Compounds do not decompose on heating. Therefore named “earths” Heavier elements compounds are more reactive and are similar to Group I (also in other respects).

Table 22.4 Some Properties of the Group 2 (Alkaline Earth) Metals: 

Table 22.4 Some Properties of the Group 2 (Alkaline Earth) Metals

Beryllium: 

Beryllium Unreactive toward air and water. BeO does not react with water, all others from hydroxides. Be and BeO dissolve in strongly basic solutions to form the BeO22- ion (therefore are acidic). BeCl2 and BeF2 melts are poor conductors: Therefore they are covalent rather than ionic solids.

Beryllium Chloride: 

Beryllium Chloride

Dow Process for Production of Mg: 

Dow Process for Production of Mg

Electrolysis of Molten MgCl2: 

Electrolysis of Molten MgCl2

Decomposition of CaCO3 (lime): 

Decomposition of CaCO3 (lime)

Stalactites and Stalagmites: 

Stalactites and Stalagmites CO2 + H2O → H3O+ + HCO3- Ka = 4.410-7 HCO3- + H2O → H3O+ + CO32- Ka = 4.710-11 CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq)

Other Compounds: 

Other Compounds Gypsum, CaSO4·2H2O: Plaster of paris CaSO4·½H2O by heating bypsum. Used in drywall. BaSO4 used in X-ray imaging . Slaked lime used in mortar: CaO absorbs water from the cement to form Ca(OH)2 which subsequently reacts with CO2 to form CaCO3.

22-3 Ions in Natural Waters: Hard Water: 

22-3 Ions in Natural Waters: Hard Water Rainwater is not chemically pure water. Contains dissolved atmospheric gases. Once on the ground it may pick up a few to about 1000 ppm of dissolved substances. If the water contains ions capable of forming a precipitate we say that the water is hard. Hardness may be permanent or temporary.

Temporary Hard Water: 

Temporary Hard Water Contains HCO3- ion. When heated gives CO32-, CO2 and H2O. The CO32- reacts with multivalent ions to form precipitates. (for example CaCO3, MgCO3) Soften water by precipitating the multivalent ions using slaked lime.

Permanent Hard Water: 

Permanent Hard Water Contains significant concentrations of anions other than carbonate. For example SO42-, HSO4-. Usually soften by precipitating the Ca2+ and Mg2+ using sodium carbonate leaving sodium salts in solution. Bathtub ring is caused by salts of Mg2+ and Ca2+ of palmitic acid (a common soluble soap).

Water Softening: 

Water Softening Ion exchange. Undesirable cations, Mg2+ Ca2+ and Fe3+ are changed for ions that are not as undesirable, ex. Na+. Resins or zeolites.

Deionizing: 

Deionizing Instead of replacing cations with Na+, they are replaced with H+. Then the anions are replaced with OH-. H+(aq) + OH-(aq) → H2O(l)

22-4 Group 13 Metals: Aluminum, Gallium, Indium and Thallium: 

22-4 Group 13 Metals: Aluminum, Gallium, Indium and Thallium

Uses : 

Uses Aluminum is most important. Third most abundant element, 8.3% by mass of crust. Lightweight alloys. Easily oxidized to Al3+. 2 Al(s) + 6 H+(aq) → 2 Al3+(aq) + 3 H2(g) 2 Al(s) + 3/2 O2(g) → Al2O3(s) ΔH = -1676 kJ 2 Al(s) + Fe2O3(s) → Al2O3(s) + Fe(s) The Thermite reaction (used in on-site welding of large objects):

Uses: 

Uses Indium. Makes low melting alloys. Low-temperature transistors and photoconductors. Thallium Extremely toxic. Few industrial uses. Tl2Ba2Ca2Cu3O8+x exhibits superconductivity up to 125K.

Oxidation States: 

Oxidation States Al almost exclusively 3+. In and Ga both 3+ and 1+. Tl both 1+ and 3+. Tl+ resembles Group 1. [Xe]4f145d106s2 – the inert pair effect.

Purification of Bauxite: 

Purification of Bauxite ppt Fe(OH)3 with OH- and filter. Make Al(OH)4- acidic with CO2. Precipitated Al(OH)3.

Production of Aluminum: 

Production of Aluminum

Aluminum Halides: 

Aluminum Halides

Aluminum and Alums: 

Aluminum and Alums

22-5 Group 14 Metals: Tin and Lead: 

22-5 Group 14 Metals: Tin and Lead Properties vary through this group. Tin and Lead are metallic +2 and +4 oxidation states  and  forms,  less stable < 13 C, tin pest or tin disease. Germanium is metalloid. Silicon, though a semiconductor is mainly nonmetallic. Carbon is a nonmetal.

Table 22.6 Some Properties of Tin and Lead (of Group 14): 

Table 22.6 Some Properties of Tin and Lead (of Group 14)

Tin and Lead Ores and Uses: 

Tin and Lead Ores and Uses Cassiterite ore, SnO2, reduced with C to Sn. Galena, PbS, roasted in air then reduced with C. Alloys of Sn Solders Bronze (90% Cu, 10% Sn Pewter (85% Sn, 7% Cu, 6% Bi, 2% Sb) Pb Pimary use in storage batteries. Radiation shields.

Oxides: 

Oxides Lead PbO, litharge, yellow (ceramics, cements, batteries). PbO2, red brown (matches, storage batteries). Pb3O4, mixed oxide known as red lead, red (metal-protecting paints). Tin SnO2 (jewelry abrasive)

Halides: 

Halides SnCl2 Good reducing agent. Quantitative analysis of iron ores. SnCl4 Formed from Sn and Cl2, obtained recovering Sn. SnF2 Anti-cavity additive to toothpaste.

Lead Poisoning: 

Lead Poisoning Extensive use of Pb in plumbing systems, utensils, pottery glazes and paints, and gasoline additives. Pb interferes with heme metabolism. Mild poisoning: Nervousness and depression. Severe poisoning: Nerve, brain and kidney damage.

Focus On Gallium Arsenide: 

Focus On Gallium Arsenide Solar Cells LEDs Diode LASERs CD systems. Fiber optic systems. Intrinsic semiconductor Tunable band gap (add P) Various emission 540-890 nm.

Chapter 22 Questions: 

Chapter 22 Questions Develop problem solving skills and base your strategy not on solutions to specific problems but on understanding. Choose a variety of problems from the text as examples. Practice good techniques and get coaching from people who have been here before.