Transition Metals - Shoreline School Elements Handbook Elements Handbook Transition Metals Catalytic

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  • R40

    Elements Handbook

    Elements HandbookHandbook

    Transition Metals

    Before 1700Au

    gold

    Ag

    silver

    Cu

    copper

    Fe

    iron

    Hg

    mercury

    Zn

    zinc

    17001799Co

    cobalt ~1735

    Pt

    platinum 1735

    Ni

    nickel 1751

    Mn

    manganese 1774

    Mo

    molybdenum 1778

    W

    tungsten 1783

    Ti

    titanium 1791

    Y

    yttrium 1794

    Cr

    chromium 1797

    18001899V

    vanadium 1801

    Nb

    niobium 1801

    Ta

    tantalum 1802

    Pd

    palladium 1803

    Rh

    rhodium 1803

    Os

    osmium 1803

    Ir

    iridum 1803

    Cd

    cadmium 1817

    Zr

    zirconium 1824

    Ru

    ruthenium 1844

    Sc

    scandium 1878

    After 1900Lu

    lutetium 1907

    Hf

    hafnium 1923

    Re

    rhenium 1925

    Physical Properties

    Most transition metals are ductile, malleable, and good conductors of heat and electric current.

    For transition metals, density and melting point tend to increase across a series or increase to a peak in Group 6B and then decrease.

    Compounds of transition metals tend to have color.

    Except for copper and gold, transition metals, including platinum, have a silvery luster.

    Sources

    Transition metals come from mineral deposits in Earths crust. Minerals that are used for the commercial production of metals are called ores.

    For centuries, people have developed techniques for separating metals from ores. The ore is concentrated and the metal removed by reduction. Then the metal is refined and purified.

    Gold exists as an element in nature. But its ore needs to be concentrated before the gold can be extracted and purified.

    Density and Melting Points of Period 4 Transition Metals

    3.0

    9.0

    0

    6.0

    Den

    sity

    (g

    /cm

    3 )

    Sc

    2.99

    Cr

    7.15

    Mn Fe Co Ni Cu Zn

    7.3 7.87

    Ti

    4.51

    V

    6.0

    8.96

    7.14

    8.86 8.90

    500

    2000

    1500

    0

    1000

    Sc

    1541

    Cr

    1907

    Mn Fe Co Ni Cu Zn

    12461538

    Ti

    1668

    V

    1910

    1084

    420

    1495 1455

    Tem

    per

    atu

    re (

    C)

    Appendix_A.fm Page 40 Friday, October 22, 2004 10:00 AM

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  • Transition Metals R41

    Atomic Properties

    Among the transition metals, as atomic number increases, there is an increase in the number of electrons in the second-to-highest occupied energy level.

    In periods 5 and 6, transition metals in the same group have identical or almost identical atomic radii. Consequently, these pairs of elements have very similar chemical properties. They tend to occur together in nature and are difficult to separate.

    Chemical Properties

    There is great variation in reactivity among transition metals. Scandium and yttrium are similar to Group 1A and 2A metals. They are easily oxidized on exposure to air and react with water to release hydrogen. Platinum and gold are extremely unreactive and resist oxidation.

    In general, transition metals have multiple oxidation states. Compounds in which the elements are in their highest oxidation states are powerful oxidizing agents.

    Most transition metals form compounds with distinctive colors. The color of a transition metal compound or solution can indicate the oxidation state of the metal.

    The oxidation number of vanadium is 5 in the yellow solution, 4 in the blue solution, 3 in the green solution, and 2 in the purple solution.

    Trends in Atomic Size for Transition Metals

    Increasing Atomic Number120

    130

    140

    150

    160

    170

    180

    190

    Ato

    mic

    rad

    ius

    (pm

    )

    Sc

    Y

    Lu

    Ti

    HfZr

    Cr

    MoW

    Tc

    Fe

    Ru

    Os

    Co Ni

    PtAu

    Ag

    Zn

    HgCd

    V

    TaNb

    Mn

    Rh

    Re IrPd

    Cu

    Oxidation Numbers of Period 4 Transition Metals

    8

    6

    4

    2

    0Sc Ti V Cr Mn Fe Co Ni Cu Zn

    Oxi

    dat

    ion

    Nu

    mb

    ers

    most common

    VO43

    Cr2O72

    MnO4

    In these aqueous solutions, vanadium, chromium, and manganese are in their highest oxidation states.

    Appendix_A.fm Page 41 Monday, June 21, 2004 6:59 AM

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  • R42 Elements Handbook

    Elements HandbookHandbook

    Transition Metals

    Catalytic Converters

    In an internal combustion engine, some hydrocarbon molecules arent completely oxidized. They form carbon monoxide instead of carbon dioxide. Some hydrocarbon molecules even pass into the exhaust without reacting. At the high temperature and pressure inside an engines cylinders, some nitrogen from the air reacts with oxygen to produce irritating nitrogen oxides.

    A catalytic converter keeps these pollutants from being released into the air. Inside the converter is a porous ceramic cylinder with a honeycomb structure. The ceramic absorbs particles of rhodium and platinum. The metals are catalysts for reac-tions that occur as exhaust gases pass through channels in the converter. Rhodium helps convert nitrogen oxides to nitrogen. Platinum helps convert hydrocarbons and carbon monoxide to carbon dioxide and water.

    Cu Copper Alloys

    Copper was one of the first metals to be widely used. It is found uncombined in nature or easily reduced from its ores. The Roman supply of copper came mainly from Cyprus and was known as aes Cyprium (metal of Cyprus). This name evolved to cyprium and then cuprium, which is why copper has the symbol Cu. Pure copper is valued both for its ability to conduct an electric current and its ability to resist corrosion.

    Around 3500 BC, people began to add tin to copper to form bronze. This alloy is harder than pure copper and easier to melt for casting. Metalworkers could produce bronze with different properties by varying the amount of tin. Bronze used to make statues might contain as little as 10% tin by mass. Bronze used to make bells would contain 1325% tin. Most copper coins are bronze with 4% tin and 1% zinc.

    Brass is an alloy of copper and zinc. Brass is harder than pure copper and more malleable than bronze. Brass containing at least 65% copper can be worked when it is cold. Brass with 5565% copper can be worked when it is hot. Before large amounts of gold and silver reached Europe in the 1500s, brass was the metal used for decorative items.

    Copper that is exposed to oxygenand water forms a patina of basiccopper salts. This thin filmprotects the underlying metalfrom further oxidation. Thecomposition of the patina, itscolor, and the rate at which itforms vary with the climate. Therate is faster near the ocean.

    When a bronze bell is struck, the clear, loud tone lasts for several seconds.

    Ceramic withPt and Rh

    Historically, brass was used to make high-quality scientific instruments. This microscope was made in 1765.

    Appendix_A.fm Page 42 Monday, June 21, 2004 6:59 AM

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  • Transition Metals R43

    Fe Iron and Steel

    Carbon is used to extract iron from its ores. At first, people used charcoal from burnt wood. In 1709, Abraham Darby invented a process that used coke instead of charcoal. Coke is almost pure carbon. It is produced when coal is heated and the impurities removed as gases. With coke, the production of iron became less expensive and more efficient.

    Iron ore is reduced to metallic iron in a blast furnace. Ore, coke, and limestone are added at the top of the furnace. Molten iron and slag collect at the bottom. The pig iron produced contains 35% carbon and smaller amounts of other impurities, which make the iron brittle. Pig iron cant be rolled or welded, but it can be cast. Cast iron is used to make stoves and engine blocks for cars.

    Most pig iron is used to make steel. The methods for making steel differ, but they all lower the carbon content to less than 2% and remove other impurities. About 90% of the steel produced is carbon steel, which contains no other metals. Mild steel, which is malleable and ductile, contains less than 0.2% carbon. Medium steel (0.2% to 0.6% carbon) is used for structural components, such as beams and girders. Because high-carbon steel (0.8% to 1.5% carbon) is harder than other carbon steels, it is used to make items such as drill bits and knives.

    Transition metals are used to produce alloy steels with a specific set of properties. The most common stainless steel contains about 18% chromium and 8% nickel.

    Iron ore typically contains Fe2O3, and SiO2. When heated, limestone produces CaO, which reacts with SiO2 to form slag. Slag is used to manufacture Portland cement.

    In 1779, Abraham Darby III built the worlds first cast-iron bridge across the River Severn in England. The bridge is still used by pedestrians.

    Insulation

    Oxygen-rich air

    Molten iron

    Slag

    Exhaust gases(CO, CO2, N2)

    Iron ore, coke,limestone

    200C

    800C

    1300C

    1900C

    Blast Furnace

    Did You Know...Did You Know...??Swords made with D

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