Types of Metals Help (page 2)
Noble Metals: Gold, Silver, And Copper
Since the first shiny speck caught the eye of early humans, gold, silver, and copper have been used for coins, jewelry, and household serving ware. Resistant to rust and corrosion, they were an excellent choice for coins, while being doubly useful by showing the local king’s face to strangers passing through the country.
Gold, a shiny yellow metal, is a good conductor of heat and electricity. It is the most malleable and ductile metal. The early alchemists based their reputations and lives on providing more of this metal to their patrons. In the western United States, gold fever affected thousands of people during the Gold Rush days of the 1800s seeking their fortunes and a better life.
Silver, a brilliant white, lustrous metal, is the best conductor of heat and electricity of all the metals. It was also prized by early peoples for its beauty and uses. Silver, less resistant to corrosion, will tarnish, turning black when it oxidizes in the air. It was thought that the state of Nevada was admitted to the Union in 1864, during the Civil War to provide funds to the Union and easier access to its resources of silver. This useful modern metal is used in coins, jewelry, electrical contacts, mirrors, circuitry, photography, and batteries.
Copper has an orange-brown color and is used in pipes, electrical wires, coins, paints, fungicides, and in alloys combined with other metals. In less developed countries, local people used copper widely for platters bowls, tools, and jewelry. Pennies, though once 100% copper, are now (since 1981) only treated on the outside with copper plating to give the United States’ one cent coin its reddish brown (copper) color. Many years ago, the badges of police officers were made from copper and so the slang expression “copper” or “cop” was commonly used.
Within the alkali metals, lithium, sodium, and potassium are known as active metals . Their reactivity increases as their atomic number increases. These elements are extremely reactive in water and air. They are frequently stored in oil to prevent explosions when accidentally mixed with water.
Lithium is the third element in the Periodic Table following helium. It is usually found in the mineral spodumene. Lithium is the lightest metal and, when isolated, so soft it can be cut with a sharp knife. The density of lithium is so low that it will float on water when laid gently on the surface. As with the rest of the alkali metals, it is very reactive in water. Generally, it is stored in oil or kerosene to prevent it from reacting. When combined with aluminum, lithium combines to form a strong alloy metal used in aircraft and spaceships.
Although they are all highly reactive, the alkali metals all have certain differences. Sodium and potassium are soft metals that are found in silicate minerals and in seawater. Rubidium and cesium are the largest and heaviest elements of the group that react explosively with water.
Like the rest of the alkali metals, cesium is silvery white when in purified form. It is commonly found in the mineral pollucite, a compound containing silicon, oxygen, and aluminum as well. Cesium is the softest metal known and melts at 29°C. When held, it will melt at body temperature, 37°C (98.6°F), like a chocolate candy in your hand. Only mercury has a lower melting point.
Alkaline Earth Metals
The Periodic Table is great for placing elements according to their characteristics. An element’s location provides information about its “personality” and uses.
Barium’s location in group IIA shows that it is an alkaline earth metal. Like calcium and magnesium, barium has applications in medicine as barium sulfate (opaque to X-rays and used to check out the digestive tract) and photography (a whitener in photographic papers). Barium helps doctors to differentiate between physiological structures.
Next in the list of commonly known metals, after gold, silver, and copper, is iron. Iron was discovered thousands of years ago and frequently used as a marker for the progress of human civilizations. This time of early discovery from pre-history until about 1100 became known as the Iron Age.
Iron, a reddish brown metal, is the “friendliest” of the metals. It readily combines with many other elements to form a huge variety of products known for their strength, since primitive times, like hand tools, cups, and plows to name just a few. Iron is the fourth most plentiful element in the Earth’s crust making up about 5% of the elements present. Currently, more than 90% of all metal refined in the world is iron.
Iron is found in several ores, the main one being hematite (Fe 2 O 3 ). Hematite has different colors and forms. The silvery black ore is used for jewelry and sometimes thought of as heavy, black “pearls.” The red form of hematite is used in paint pigments and is known as the color, red ocher.
Other metals, such as chromium, manganese, nickel, tungsten, cobalt, and chromium, combine with iron to make steel, an alloy of superior strength, hardness, and durability. About 99% of all iron mined in the world today goes into the manufacture of steel.
Alloys are formed by the combination of two or more metals or a metal and non-metal.
When iron is coated with zinc, it is resistant to the rusting effects of oxygen and is said to be galvanized . Nails, wire, and large sheets of metal are treated this way to increase the life and use of such metals.
By mixing metals of different characteristics, in different proportions, a new metal or metal alloy can be created. The metals are melted together into a molten solution, cooled, and allowed to become solid again. The newly formed solid has the characteristics of its parent metals along with new properties, such as greater strength than either of its parents. (Example: steel = 80% iron, 12% chromium, 8% nickel; alloy manganese steel = 87% iron, 12% manganese, 1% carbon (railroad rails). Iron alloys are made by mixing together two or more molten metals and a non-metal. When producing 10-carat, 14-carat, and 18-carat gold, various percentages of gold, copper, and silver are used. Table 12.2 gives examples of commonly used alloys and their composition.
Mercury is prized by scientists for its ability to dissolve other metals and form alloys. When combined with silver, dentists make a silver-mercury amalgam (alloy) to fill cavities in teeth. Mercury also dissolves gold and is used in the collection of gold from other ores.
Practice problems for these concepts can be found at – Chemistry and Metals Practice Test
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