Metals Help (page 2)
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.
Inner Transition Metals
The 30 elements of the inner transition elements are divided into two groups and called the actinide and lanthanide series.
The actinide series are difficult to isolate since they are highly unstable and experience radioactive decay. They also show a number of oxidation states. Uranium, for example, has compounds in each of the +3, +4, +5, and +6 oxidation states.
The lanthanide elements have electron configurations within the 4f and 5d energy levels. At these high energy levels, electron configuration is fairly theoretical. The lanthanides form 3+ ions as they go into an ionized state. It is assumed that ions are formed by losing the 6s 2 and 5d 1 (or 4f if 5d is not present) electrons. These metals are very similar to each other in their chemical properties. The lanthanide metals are shiny and are affected by water and acids.
Metalloids are elements that have the properties of both metals and non-metals. Metalloids are also referred to as “semi-metals” and are located on the stair step borderline of the Periodic Table between metals and non-metals. The metalloids are made up of boron, silicon, germanium, arsenic, antimony, tellurium, and polonium.
Silicon, the second most abundant element in the Earth’s crust after oxygen, is found in granite, quartz, clay, and sand. At its most basic form, silicon has the same crystalline structure as a diamond. Maybe that is why when you walk along the beach and the sun is high, grains of sand seem to glisten like diamonds!
Silicon is used in semiconductors to carry an electrical charge. Silicon’s natural conducting capacity is further increased when small amounts of arsenic or boron are added to it. Arsenic has one more valence electron than silicon and when it is mixed with silicon, this extra electron wanders around the crystal unattached and able to conduct electricity.
Figure 12.2 shows the location is metals and metalloids in the Periodic Table.
Put simply, elements that are not metals are non-metals. Non-metals are found at the far right-hand side of the Periodic Table and consist of only eighteen elements (counting from hydrogen with the non-metals to the right). Six of these elements are the noble gases in group VIII in the far right column. Non-metals are generally gases or solids that do not conduct heat or electricity well. Some non-metals, like diamonds (a stable crystalline form of carbon), are very hard and unreactive, while others, like chlorine, have free electrons and are more reactive. Non-metals are not lustrous and are not malleable or ductile. Eleven of the non-metals are gases, one is a liquid, and six are solids. Figure 12.3 shows non-metals in solid, liquid, and gaseous forms.
Non-metals are described as elements without metallic properties. They are poor conductors of heat and electricity and are not magnetic like iron.
Noble gases are non-metals and exist as individual atoms such as neon and argon. Other non-metals are two-atom molecules, such as hydrogen, nitrogen, and oxygen.
Fluorine is at the top of the column (VIIA) in the Periodic Table known as the halogens or “salt formers.” Chlorine, bromine, iodine, and astatine are also in the halogen group. Halogens easily accept electrons from other atoms and combine with metals to form salts. In nature, fluorine is found in ores of fluorspar (calcium fluoride) and cryolite (a combination of sodium, fluorine, and aluminum). In the body, fluorine is found in the blood, bones, and teeth. Many communities in the United States add small amounts of fluorine to drinking water, since the presence of fluorine has been found to prevent the formation of cavities in teeth.
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