154 | The History and Use of Our Earth’s Chemical Elements Chemically, tungsten is rather inert, but it will form compounds with several other ele-
154 | The History and Use of Our Earth’s Chemical Elements Chemically, tungsten is rather inert, but it will form compounds with several other ele-
ments at high temperatures (e.g., the halogens, carbon, boron, silicon, nitrogen, and oxygen). Tungsten will corrode in seawater.
AbundanceandSource Tungsten is the 58th most abundant element found on Earth. It is never found in 100%
pure form in nature. Its major ore is called wolframite or tungsten tetroxide, (Fe,Mn)WO 4 , which is a mixture of iron and manganese and tungsten oxide. During processing, the ore is pulverized and treated with strong alkalis resulting in tungsten trioxide (WO 3 ), which is then heated (reduced) with carbon to remove the oxygen. This results in a variety of bright color changes and ends up as a rather pure form of tungsten metal: 2WO 3 + 3C → 2WO + 3CO 2 . Or, if hydrogen is used as the reducing agent, a more pure form of metal is produced: WO 3 + 3H 2 → W + 3H 2 O.
Tungsten ores (oxides) are found in Russia, China, South America, Thailand, and Canada. In the United States, the ores are found in Texas, New Mexico, Colorado, California, Arizona, and Nebraska. Today, it is estimated that about 75% of all tungsten is found in China.
The tungsten ore called “scheelite” is named after Carl Wilhelm Scheele (1742–1786), who studied and experimented with tungsten minerals, but as with many of his other “near” discoveries, such as oxygen, fluorine, hydrogen sulfide, hydrogen cyanide, and manganese, he was not given credit.
History In the mid-1700s a number of scientists experimented with and attempted to isolate
element 74 by treating ores of other metals with reagents. One problem was that tungsten was often confused with tin and arsenic. It was not until 1783 that Don Fausto de Elhuyar (1755–1833) and his brother Don Juan Jose de Elhuyar isolated a substance from tin ore that they called “wolframite.” They named it after the mineral in which it was found. At about the same time the Swedish named it tung sten, which means “heavy stone” in Swedish. This explains the potentially confusing use of W for the symbol for tungsten.
CommonUses Since its melting temperature is over 3,400°C, tungsten is one of the few metals that can
glow white hot when heated without melting. This factor makes it the second most frequently used industrial metal (the first is iron). Tungsten is used in the filaments of common light bulbs, as well as in TV tubes, cathode ray tubes, and computer monitors. Its ability to be “pulled” into thin wire makes it useful in the electronics industry. It is also used in solar energy products and X-ray equipment. Its ability to withstand high temperatures makes it ideal for rocket engines and electric-heater filaments of all kinds. Tungsten carbide is used as a substitute for diamonds for drills and grinding equipment. This attribute is important in the manufacture of exceptionally hard, high-speed cutting tools.
ExamplesofCompounds Most of tungsten’s stable compounds have the main oxidation state of +6 (e.g., W 6+ + 6Cl 1-
→ WCl 6 ), and the lower oxidation state of +4 occurs in the hard tungsten carbide (e.g., W 4+
155 Tungsten carbide (WC) is extremely hard and resistant to high temperatures. When cement-
Guide to the Elements |
ed to tools, it is as hard as corundum (aluminum oxide) and makes excellent grinding surfaces and cutting edges for machine tools. Tungsten disulfide (WS 2 ) is used as a solid lubricant that can withstand high temperatures. It is also used as a spray lubricant. Tungsten oxide (WO 3 ) is used to make tungsten alloys. Tungsten oxide is also used as fire- proofing for various surfaces and is used as a yellow pigment in ceramics. Tungsten steel is an alloy that acts somewhat like molybdenum to form important steel alloys; tungsten steel is tough and hard, wears well, resists rusting, and will take a sharp cut- ting edge.
Tungsten compounds of calcium and magnesium have phosphorescent properties that make them useful in manufacturing fluorescent lighting fixtures.
Hazards: Tungsten dust, powder, and fine particles will explode, sometimes spontaneously, in air.
The dust of many of tungsten’s compounds is toxic if inhaled or ingested. RHENIUM
SYMBOL:Re PERIOD:6 GROUP:7(VIIB) ATOMICNO:75 ATOMICMASS:186.207amu VALENCE:4,6,and7 OXIDATIONSTATE:+4.+6,and
+7 NATURALSTATE:Solid ORIGINOFNAME: DerivedfromtheLatinwordRhenus,whichstandsfortheRhineRiver inWesternEurope. ISOTOPES:Thereare45isotopesofrhenium.Onlyoneoftheseisstable:Re-185,which contributes37.40%tothetotalamountofrheniumfoundonEarth.Re-187,whichis radioactivewithaverylonghalf-lifeof4.35×10 +10 years,contributes62.60%torheni- um’sexistenceonEarth.Theremaining43isotopesareradioactivewithrelativelyshort half-livesandareartificiallymanufactured.
ELECTRONCONFIGURATION EnergyLevels/Shells/Electrons Orbitals/Electrons
s2,p6
3-M=18
s2,p6,d10