SCI 401 General Chemistry: Metals (PDF)

SCI 401 GENERAL CHEMISTRY  Chemistry of Engineering Materials: Metals Introduction to Metals Occurrence of Metals Metallurgy Band Theory of Electrical Conductivity The Alkali and Alkaline Earth Metals Aluminum Transition Metals  LEARNING OBJECTIVE ► I...

SCI 401 GENERAL CHEMISTRY  Chemistry of Engineering Materials: Metals Introduction to Metals Occurrence of Metals Metallurgy Band Theory of Electrical Conductivity The Alkali and Alkaline Earth Metals Aluminum Transition Metals  LEARNING OBJECTIVE ► Introduce Metal ► Describe the occurrence and abundance of metals in the Earth’s crust. ► Explain the processes involve in the metallurgy ► Explain the concept of the Band Theory of Electrical Conductivity ► Discuss the periodic trends of some metals and their reactivity.  Metal Metal is an element, compound or alloy that is a good conductor of both electricity and heat. Metal crystal structure and specific metal properties are determined by holding together the atoms of a metal. https://www.youtube.com/watch?v=vOuFTuvf4qk  Metal With the exception of hydrogen, all elements that form positive ions by losing electrons during chemical reactions are called metals. They are characterized by bright luster, hardness, ability to resonate sound and are excellent conductors of heat and electricity. Metals are solids under normal conditions except for Mercury. Metal  Physical Properties of Metal State: Metals are solids at room temperature with the exception of Hg, which is liquid at room temperature (Ga is liquid on hot days). Luster: Metals have the quality of reflecting light from their surface and can be polished e.g., Au, Ag and Cu. Malleability: Metals have the ability to withstand hammering and can be made into thin sheets known as foils. E.g., a sugar cube sized chunk of gold can be pounded into a thin sheet that will cover a football field.  Physical Properties of Metal Ductility: Metals can be drawn into wires. For example, 100 g of silver can be drawn into a thin wire about 200 meters long. Hardness: All metals are hard except sodium and potassium, which are soft and can be cut with a knife. Valency: Metals typically have 1 to 3 electrons in the outermost shell of their atoms.  Physical Properties of Metal Conduction: Metals are good conductors because they have free electrons. Silver and copper are the two best conductors of heat and electricity. Lead is the poorest conductor of heat. Bismuth, mercury and iron are also poor conductors. Density: Metals have high density and are very heavy. Iridium and osmium have the highest densities whereas lithium has the lowest density. Melting and Boiling Points: Metals have high melting and boiling points. Tungsten has the highest melting and boiling points whereas mercury has the lowest. Sodium and potassium also have low melting points.  Chemical Properties of Metal Electropositive Character: Metals tend to have low ionization energies, and typically lose electrons (i.e. are oxidized) when they undergo chemical reactions. They normally do not accept electrons. For example: Alkali metals are always 1+ (lose the electron in s subshell) Alkaline earth metals are always 2+ (lose both electrons in s subshell) Transition metal ions do not follow an obvious pattern, 2+ is common (lose both electrons in s subshell), and 1+ and 3+ are also observed Chemical Properties of Metal  Chemistry of Engineering Materials: Metals Introduction to Metals Occurrence of Metals Metallurgy Band Theory of Electrical Conductivity The Alkali and Alkaline Earth Metals Aluminum Transition Metals Occurrence of Metal  Occurrence of Metal Clay (mineral of Aluminum) Bauxite (principal ore of Aluminum) Occurrence of Metal Manganese nodule Principal Types of Minerals  Chemistry of Engineering Materials: Metals Introduction to Metals Occurrence of Metals Metallurgy Band Theory of Electrical Conductivity The Alkali and Alkaline Earth Metals Aluminum Transition Metals Metallurgy Principal steps Production of metal Production of metal Blast Furnace Production of metal Principal steps Metallurgy  Chemistry of Engineering Materials: Metals Introduction to Metals Occurrence of Metals Metallurgy Band Theory of Electrical Conductivity The Alkali and Alkaline Earth Metals Aluminum Transition Metals Band Theory of Electrical Conductivity ► In solid-state physics, the band structure of a solid describes those ranges of energy, called energy bands, that an electron within the solid may have (“allowed bands”) and ranges of energy called band gaps (“forbidden bands”), which it may not have. ► Band theory models the behavior of electrons in solids by postulating the existence of energy bands.  Band Theory of Electrical Conductivity Band theory - a model use to study metallic bonding ⮚ states that delocalized electrons move freely through “bands” formed by overlapping molecular orbitals. This theory can also be applied to certain elements that are semiconductors. Semiconductors  Semiconductors Semiconductors are materials that have properties in between those of normal conductors and insulators; they are often produced by doping.  Semiconductors Semiconductors are materials that have properties of both normal conductors and insulators. Semiconductors fall into two broad categories: Intrinsic semiconductors - composed of only one kind of material; silicon and germanium are two examples. These are also called undoped semiconductors or i-type semiconductors.  Semiconductors Extrinsic Semiconductors - are intrinsic semiconductors with other substances added to alter their properties — that is to say, they have been doped with another element. There are two types of extrinsic semiconductors that result from doping: 1. n-type for negative, from group V, such as phosphorus 2. p-type for positive, from group III, such as boron.  Extrinsic semiconductors N-Type Semiconductors are a type of extrinsic semiconductor in which the dopant atoms are capable of providing extra conduction electrons to the host material (e.g., phosphorus in silicon). This creates an excess of negative (n-type) electron charge carriers. P-Type Semiconductors are a type of extrinsic semiconductor in which the atoms have one fewer electron (e.g., boron).  Chemistry of Engineering Materials: Metals Introduction to Metals Occurrence of Metals Metallurgy Band Theory of Electrical Conductivity The Alkali and Alkaline Earth Metals Aluminum Transition Metals  Alkali metals ⮚ Chemical elements found in Group 1 of the periodic table. They appear silvery and can be cut with a plastic knife. ⮚ The alkali metals include: lithium, sodium, potassium, rubidium, cesium, and francium. ⮚ Hydrogen is not technically an alkali metal since it rarely exhibits similar behavior. ⮚ The word "alkali" received its name from the Arabic word "al qali," meaning "from ashes", which since these elements react with water to form hydroxide ions, creating alkaline solutions (pH>7). Alkali metals  Common properties of Alkali metals ⮚ The most electropositive or the least electronegative elements ⮚ Common oxidation state +1 ⮚ Found dissolved in seawater due to geologic erosion of minerals ⮚ All the discovered alkali metals occur in nature. ⮚ These metals have a BCC structure with low packing efficiency. ⮚ Low melting point. Lithium - lightest known metal and has great chemical reactivity. Do not occur free in elemental form, are combined in halides, sulfates, carbonates and silicates Alkaline Earth Metals  Alkaline Earth Metals ⮚ Less electropositive and less reactive than Group IA ⮚ Common oxidation state +2 ⮚ IIA Metals attain stable electron configuration of the preceding noble gases ⮚ Have much higher melting points than the alkali metals, harder metals than the Group 1A elements, but are soft and lightweight compared to many of the transition metals. ⮚ The chemistry of radium is not well established due to its radioactivity.  Alkaline Earth Metals Emerald is a variety of beryl, a mineral that contains the alkaline earth metal beryllium. Beryllium only occurs naturally in combination with other elements in minerals.  Chemistry of Engineering Materials: Metals Introduction to Metals Occurrence of Metals Metallurgy Band Theory of Electrical Conductivity The Alkali and Alkaline Earth Metals Aluminum Transition Metals  Aluminum Most abundant metal and the 3rd most plentiful element in the Earth’s crust. Elemental form doesn’t occur in nature Principal ore: Bauxite (Al2O3 H2O) Other minerals containing aluminum are orthoclase (KAlSi3O8), beryl (Be3Al2Si6O18), cryolite (Na3AlF6), and corundum (Al2O3). Considered a precious metal until Hall developed a method of Aluminum Charles Hall, pioneer of production development of Aluminum production  Preparation of Aluminum Anhydrous aluminum oxide (Al2O3 or corundum) is reduced to aluminum by the Hall process. The cathode is also made of carbon and constitutes the lining inside the cell. The key to the Hall process is the use of cryolite, or Na3AlF6 (melting point is 1000°C), as the solvent for aluminum oxide (melting point is 2045°C). The mixture is electrolyzed to produce aluminum and oxygen gas. Oxygen gas reacts with the carbon anodes to form carbon monoxide, which escapes as a gas.  Preparation of Aluminum The liquid aluminum metal (melting point is 660.2°C) sinks to the bottom of the vessel, from which it can be drained from time to time during the procedure.  Recycling of Aluminum ⮚ Aluminum is one of the most recycled and most recyclable materials on the market today. Nearly 75% of all aluminum produced in the U.S. is still in use today. ⮚ Aluminum can be recycled directly back into itself over and over again in a true closed loop. ⮚ Recycling aluminum costs 95% less energy compared to producing primary aluminum. Recycling of Aluminum  Chemistry of Engineering Materials: Metals Introduction to Metals Occurrence of Metals Metallurgy Band Theory of Electrical Conductivity The Alkali and Alkaline Earth Metals Aluminum Transition Metals  Transition Metals Transition Metal – any of various chemical elements that have valence electrons—i.e., electrons that can participate in the formation of chemical bonds—in two shells instead of only one. —Transition elements are the elements that are found in Groups 3-12 (old groups IIA-IIB) on the periodic table. — Transition metals typically have incompletely filled d subshells or readily give rise to ions with incompletely filled d subshells. — Many transition element compounds are brightly colored due to the inner-level d electron transitions.  Properties of Transition metal Transition metals have similar properties, and some of these properties are different from those of the metals in group 1. Physical properties — they are good conductors of heat and electricity — they can be hammered or bent into shape easily — they have high melting points (but mercury is a liquid at room temperature) — they are usually hard and tough — they have high densities  Properties of Transition metal Chemical properties The transition metals have the following chemical properties in common: — they are less reactive than alkali metals such as sodium — they form colored ions of different charges — some are very unreactive (silver and gold) — many are used as catalysts  Uses of transition metals Transition metals have a wide range of uses. Their properties are very similar but not identical. It is important to choose the right transition metal for the required purpose. GOLD  Uses of transition metals SILVER COPPER  Uses of transition metals IRON Iron is usually too soft to be used as the metal alone. It is usually mixed with small amounts of other elements to make steels, which are harder and stronger than iron, but easily shaped. However, iron and steel react slowly with water and air to produce rust. They must be protected with, for example, a layer of paint.  Uses of transition metals CHROMIUM  Supplementary videos ► https://www.youtube.com/watch?v=vOuFTuvf4qk ► https://www.youtube.com/watch?v=kCM2mSb4qIU ► https://www.youtube.com/watch?v=CmiitvJiCPc ► https://www.youtube.com/watch?v=8qh5myTmcRs