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Types of Metals Help

By — McGraw-Hill Professional
Updated on Aug 28, 2011

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.

Alkali Metals

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.

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