Chapter 21 - Metallurgy and the Chemistry of Metals

21.1 - Occurrence of Metals

• Minerals provide the majority of metals.
• A mineral is a naturally occurring substance that can have a wide variety of chemical compositions.
  • Ore is a mineral deposit that is concentrated enough to allow for the economic recovery of the desired metal.
• Aluminum, iron, calcium, magnesium, sodium, potassium, titanium and manganese are the most abundant metals that exist in Earth crust as minerals.
• Seawater has many metal ions, including Na+, Mg2+ and Ca2+, which are rich.
  • Moreover, vast areas of the ocean floor are covered with manganese nodules, mainly made of manganese and chemically combined iron, nickel, copper, and cobalt.

21.2 - Metallurgical Processes

• The science and technology of separating metals from their ores and creating alloys is known as metallurgy.
  • A solid solution of two or more metals, or a metal or metals with one or more nonmetals, is known as an alloy.
• Magnets have a strong attraction to ferromagnetic metals.
  • A powerful electromagnet can be used to remove the mineral magnetite (Fe3O4) from the gangue.
  • Another ferromagnetic metal is cobalt.
• Mercury may combine with a variety of metals to generate amalgams.
  • A mercury amalgam is a mixture of mercury and one or more additional metals.
• Pyrometallurgy, or procedures carried out at high temperatures, is now used in the majority of key metallurgical processes.
  • Chemical or electrolytic methods can be used to reduce the size of these procedures.

21.3 - Band Theory of Electrical Conductivity

• Metallic bonding is based on band theory, which asserts that delocalized electrons can easily flow through "bands" created by overlapping molecular orbitals.
• Several elements are semiconductors, which means that they are generally not conductors but can conduct electricity at high temperatures or when mixed with a little number of other elements.
• Because they give conduction electrons, these impurities are known as donor impurities.
  • N-type semiconductors are solids that include donor impurities, where n stands for negative.
• P-type semiconductors are those that contain acceptor impurities, with the letter p standing for positive.
  • Acceptor impurities are those that are lacking in electrons.

21.4 - Periodic Trends in Metallic Properties

• Metals are shiny, solid at normal temperature, have good heat, the characteristics conductors, malleable, and ductile.
• The metallic nature of metals increases from right to right through a period and from top to bottom within a group in just the opposite directions.
• Metals tend to form cations and almost always have positive numbers of oxidation in their compounds, because they generally are lowly electronegativity.
  • However, beryllium and magnesium form covalent compounds in Group 2A and in Group 3A metals.

21.5 - The Alkali Metals

• The melting temperatures of alkali metals are low, and they are soft enough to be cut with a knife.

  • These metals all have a crystal structure that is body-centered and has a low packing efficiency.

• Alkali metals are found in combination with halide, sulfate, carbonate, and silicate ions and are never found in their elemental form.

• The nature of sodium and potassium is about equal.

  • In silicate minerals like albite (NaAlSi3O8) and orthoclasses they occur (KAlSi3O8).

• Silicate minerals are slowly decomposed by wind and rain and are converted to more soluble compounds over a long period.

• These compounds are finally leached from the ground and carried to the sea by rain.

  • However, if we look at the marine water composition, the sodium/potassium concentration ratio is around 28 to 1.

  

21.6 - The Alkaline Earth Metals

• It's mostly used as an alloying agent for metals like aluminum and copper, as well as to make beryllium metal from its compounds.
• Calcium is a necessary component of all living things.
  • The calcium ion is present in a complex phosphate salt, hydroxyapatite, Ca5(PO4)3OH, which is the main component of bones and teeth.
• Magnesium oxide react very slowly with water to magnesium hydroxide in a White Solid Suspension called Magnesium Milk.

21.7 - Aluminum

• In the Earth's crust, aluminum is the most abundant metal and the third most abundant element.
  • The elemental form does not exist in nature; bauxite is the primary resource.
• Bauxite, which is commonly polluted with silica (SiO2), iron oxides, and titanium(IV) oxide, is used to make aluminum.
• The Hall process reduces anhydrous aluminum oxide, or corundum, to aluminum.
• The exothermic enthalpy of production of aluminum oxide is quite high (Hf ° = 1670 kJ/mol).
  • Aluminum is suitable for use in solid propellants for rockets, such as those used in some space shuttles, because of its characteristic.