Introduction to Metals
For thousands of years, humans have used metals as tools and weapons. They experimented with many native ores to make the best use of what they had. Of all the elements in the Periodic Table, the best known are the metals.
Ancient peoples found that when a very soft metal, like copper, was mixed with zinc and nickel, a harder and stronger metal, called bronze, was formed. This metal was used so much for cutting tools and other utensils that the years between 4,000 and 1,100 were called the Bronze Age.
We have all seen pictures of gold miners who have worked for years in dimly lit mines searching for deposits of gold that would “make their fortunes.” Others spent their days from morning until night hunched over icy mountain streams panning handfuls of dirt and gravel and watching for the bright glint of a single metal nugget. Even today, people get excited over flecks of gold (iron sulfide, FeS 2 ) found in rock. Elements are commonly divided between either metals or non-metals.
Unlike gold and silver, which are pure elements, many metals are not found in nature as a single element. Most metals are combined with other elements within ores that must be processed to extract their different parts. Table 12.1 gives some examples of different ores and the metals they contain.
Pure metals are separated from ores primarily with heat. This is done in a high-temperature blast furnace. By adding reactants like limestone and coke (a carbon residue) to break hydrogen bonding and release the bonded metals, individual metals can be collected. Figure 12.1 shows a simple blast furnace.
Lead, though sometimes found as a pure metal in nature, is usually found as the ore galena or lead sulfide. Lead ore is crushed, heated in a blast furnace, and then extracted. Most lead produced in the United States is used for battery and battery electrodes as well as lead solder used in making connections on computer circuit boards.
Mercury is most often found in nature as the ore, cinnabar. Cinnabar (HgS), also called vermillion, is a bright red mineral crushed and used to make the red paint pigment used by Renaissance painters.
The metal bismuth is most often found as the ores bismite (bismuth oxide, a yellow pigment in cosmetics) and bismuth glance (bismuth sulfide). It is commonly combined with lead, tin, and copper and so is extracted along with these metals. Bismuth is used in the treatment of ulcers by acting as an antacid. Like water, bismuth expands when it changes from a liquid to a solid.
Metals form large crystalline structures with high boiling and melting points. These structures are made up of metal ions. The extra electrons within the outer shells of metal atoms are still able to move around within the crystalline structures and in turn, cause the solids to be good conductors.
You can think of the structure as being like a vegetable soup, with the “broth” made up of the electrons, and the “vegetables” consisting of a lattice of positively charged metal ions. The broth does not have enough electrons to form individual bonds between atoms, so sharing electrons is a much more efficient form of bonding. The bonding is stronger and the metallic crystal is harder, as the ions are held more tightly between atoms that have more outer orbital electrons to share in the “broth.” Transition metals with more electrons in their outer shell orbits are denser than alkali metals with fewer electrons in their outer shells.
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