1. Chemistry of the Metallic Elements
Valentim M. B. Nunes
Engineering Unit – Chemistry Section
April 2018

2. Elements
We saw previously that all the elements can be classified as metallic, non-metallic or metalloids. Until now, we also studied fundamental theories of Chemistry, like the nature of chemical bond, intermolecular forces, chemical equilibrium, electrochemistry, etc. All that knowledge is necessary to understand the chemistry of the elements, in particular metals.
This Descriptive Inorganic Chemistry is necessary to understand the utility and application of chemistry in several industrial and biological processes (including live organisms)

3. Occurrence
Most of metals are obtained from minerals. A mineral its a substance that occurs naturally with a well defined composition. A mineral deposit is called ore

4. Metallurgic processes
Metallurgy is the science of separation of metals from minerals and the production of metals and metallic alloys. It involves: a) preparation of the ore; b) production of metals; c) purification.
The production of a free metal is always a reduction process. Sometimes is necessary the previously calcination of the ore to expel volatile impurities. 
CaCO3(s)  CaO(s) + CO2(g)
2 PbS(s) + 3 O2(g)  2 PbO(s) + 2 SO2(g)
The most important processes occurs at high temperatures a process known by pyrometallurgy.

5. Electrolytic reduction of chloride. 2 MCl  2 M + Cl2
Reduction Processes
Metal
Li, Na, Mg, Ca
Electrolytic reduction of chloride.
2 MCl  2 M + Cl2 Al
Electrolytic reduction of the oxides.
Cr, Mn, Ti, V, Fe, Zn
Reduction of the metallic oxide with a metal with lower Eº or with carbon and CO.
Hg, Ag, Pt, Cu, Au
Non combined or calcination with sulphides.
Eº(V)

6. Metallurgy of Iron
Iron exists in certain minerals like pyrite (FeS) or hematite (Fe2O3). The process involves the chemical reduction of the minerals by carbon (in coke) in a blast furnace.
3 Fe2O3 + CO  2 Fe3O4 + CO2
CaCO3  CaO + CO2
Fe3O4 + CO  3 FeO + CO2
C + CO2  2 CO
FeO + CO  Fe + CO2
2 C + O2  2 CO
cast iron

7. Production of steel
The production of steel is a fundamental industry. While the iron production is a process of reducing the conversion in steel is a process of oxidation. The impurities are removed with oxygen gas.
CaO or SiO2
CO2, SO2
(pollution!)

8. Metallic Purification
Distillation: metals with low melting points can be purified by fractional distillation. Example: the Mond method for the purification of nickel.
Ni(s) + 4 CO(g) Ni(CO)4(g) Tetranickelcarbonyl
43 ºC
200 ºC
Electrolysis: Cooper (already studied)
Zone refining.

9. Alkali Metals
They are the less electronegative elements . The oxidation state is +1. They have low melting point and low density.

10. Occurrence: NaAlSi3O8 (albite); NaCl; NaNO3(Chile nitrate)
Sodium, Na
Occurrence: NaAlSi3O8 (albite); NaCl; NaNO3(Chile nitrate)
Obtaining: electrolysis of molten NaCl (Downs cell)
Principal reactions:
2 Na(s) + 2 H2O(l)  2 NaOH(aq) + H2(g)
2 Na(s) + O2(g)  Na2O2(g)
Na2O2(g) + 2 H2O(l)  2 NaOH(aq) + H2O2 (aq)

11. Occurrence: KAlSi3O8 (orthoclase); KCl
Potassium, K
Occurrence: KAlSi3O8 (orthoclase); KCl
Obtaining: distillation of molten KCl at 892 ºC.
Principal reactions:
2 K(s) + 2 H2O(l)  2 KOH (aq) + H2(g)
K (s) + O2 (g)  KO2 (g)
2 KO2 (g) + 2 H2O (l)  2 KOH (aq) + O2 (g) + H2O2 (aq)
4 KO2 (g) + 2 CO2 (g)  2 K2CO3 (s) + 3 O2 (g)

12. Applications
Na2CO3: water treatment; soaps production; detergents; medicines, glass industry, etc.
Nitrates: fertilizers; explosives, .....
Hydroxides: soaps production; electrolytes for batteries, ....
Others

13. Alkaline earth metals: Magnesium, Mg
Occurrence: Mg(OH)2 (brucite); CaCO3.MgCO3 (dolomite); MgSO4.7 H2O (epsomite).
Obtaining: electrolysis of molten MgCl2 (obtained from sea water)
Principal reactions:
Mg (s) + H2O (g)  MgO (s) + H2 (g)
2 Mg (s) + O2 (g)  2 MgO (s)
3 Mg (s) + N2 (g)  Mg3N2 (s)
MgO (s) + H2O (l)  Mg(OH)2 (aq)

14. Obtaining: electrolysis of molten CaCl2
Calcium, Ca
Occurrence: CaCO3 (limestone, chalk and marble); CaSO4.2 H2O (plaster); CaF2 (fluorite)
Obtaining: electrolysis of molten CaCl2
Principal reactions:
Ca (s) + H2O (l)  Ca(OH)2 (aq) + H2 (g)
CaCO3 (s)  CaO (s) + CO2 (g)
CaO (s) + H2O (l)  Ca(OH)2 (s)

15. Applications
Magnesium : metallic alloys, cathodic protection, batteries....
CaO: metallurgy, SO2 removing (gases treatment), soil acidity adjustment,.....
Ca(OH)2: water treatment.
Others

16. 2 Al (s) + 6 HCl (aq)  2 AlCl3 (aq) + 3 H2 (g)
Aluminum, Al
Aluminum is the most abundant metal and the 3rd most abundant element in the Earth's crust (7.5%). It has low density, high tensile strength and its an excellent electrical conductor.
Occurrence: Al2O3. 2 H2O (bauxite); Be3Al2Si6O18 (beryl); Na3AlF6 (criolite); Al2O3 (corundum).
Obtaining: electrolysis of anhydrous alumina by the Hall-Héroult process.
                         
Principal reactions:
2 Al (s) + 6 HCl (aq)  2 AlCl3 (aq) + 3 H2 (g)
2 Al (s) + 2 NaOH (aq) + 2 H2O (l)  2 NaAlO2 (aq) + 3 H2(g)
4 Al (s) + 3 O2 (g)  2 Al2O3 (s)

17. Applications
High voltage transmission lines; aeronautics engineering; recipients; solid propulsion in rockets.

18. Recycling
Recycling: Aluminum is used in millions of tons of cans of soft drinks. To recycle aluminum its only necessary the energy to heat and fuse Al ( ~10.7 kJ/mol). In total the to recycle one mole of aluminum is only about 9% the energy necessary to produce the same amount by electrolysis.