[AK-TIN'-EE-UHM] ╘HE CHEMICAL ELEMENT ACTINIUM IS A RADIOACTIVE METAL, THE FIRST MEMBER OF THE ┴CTINIDE SERIES. ╔TS SYMBOL IS ┴C, ITS ATOMIC NUMBER 89, AND ITS ATOMIC WEIGHT 227 (MOST STABLE ISOTOPE). ┴CTINIUM WAS DISCOVERED IN 1899 BY ┴. ─EBIERNE, WHO FOUND IT IN PITCHBLENDE RESIDUES. ═ANY RADIOACTIVE ISOTOPES OF ACTINIUM ARE KNOWN, ONE OF WHICH, ┴C-227 HAS A ╚┴╠╞-╠╔╞┼ OF 21.6 YEARS AND IS PRESENT IN NATURAL URANIUM. ╘HE OTHER ISOTOPES HAVE HALF-LIVES OF 10 DAYS TO LESS THAN 5 SECONDS.
┴LUMINUM
┴LUMINUM, SYMBOL ┴L, IS A SILVERY-WHITE METAL IN ╟ROUP ╔╔╔┴ OF THE PERIODIC TABLE. ╔TS ATOMIC NUMBER IS 13, ITS ATOMIC WEIGHT 26.9815. ╔T IS DUCTILE, NONMAGNETIC, AND AN EXCELLENT CONDUCTOR OF HEAT AND ELECTRICITY. ╘HE DENSITY OF ALUMINUM AT 20 DEG ├ IS 2.699 G/CU CM (0.1 LB/CU IN); IT MELTS AT 660.24 DEG ├ AND BOILS AT 2,450 DEG ├. ┴LUMINUM IS WIDELY USED IN MANY KINDS OF PRODUCTS BECAUSE A COMBINATION OF PROPERTIES GIVES IT SPECIAL ADVANTAGES OVER OTHER MATERIALS.
┴MERICIUM
[AM-UH-RIS'-EE-UHM] ┴MERICIUM IS A ╘RANSURANIUM ELEMENT, A RADIOACTIVE METAL OF THE ┴CTINIDE SERIES. ╔TS SYMBOL IS ┴M, ITS ATOMIC NUMBER IS 95, AND THE ATOMIC WEIGHT OF ITS STABLEST ISOTOPE IS 243. ┴MERICIUM DOES NOT OCCUR NATURALLY. ╔T WAS SYNTHESIZED FOR THE FIRST TIME BY ╟LENN ╙EABORG, ┴. ╟HIORSO, ╥. ┴. ╩AMES, AND ╠. ╧. ═ORGAN IN 1944. ╘HEY BOMBARDED PLUTONIUM-239 WITH HELIUM IONS AND OBTAINED THE ISOTOPE ┴M-241. ╘HE KNOWN ISOTOPES OF AMERICIUM, WHOSE MASS NUMBERS RANGE FROM 237 TO 246, ARE RADIOACTIVE. ╘HE STABLEST ISOTOPE, ┴M-243, HAS A HALF-LIFE OF 7,370 YEARS. ╒SABLE AMOUNTS OF ┴M-241 ARE OBTAINED BY BOMBARDMENT OF PLUTONIUM-241 IN NUCLEAR REACTORS. ┴MERICIUM IS FAIRLY REACTIVE: IT COMBINES WITH OXYGEN WHEN EXPOSED TO AIR. ┬ECAUSE IT EMITS STRONG GAMMA RADIATION, ┴M-241 IS USED IN VARIOUS TYPES OF MEASURING DEVICES AND IN RADIOGRAPHY.
┴NTIMONY
[AN'-TI-MOH-NEE] ╘HE CHEMICAL ELEMENT ANTIMONY IS A BRITTLE SILVER-WHITE METAL. ╔TS CHEMICAL SYMBOL IS ╙B, ATOMIC NUMBER 51, AND ATOMIC WEIGHT 121.75. ╘HE ELEMENT AND SOME OF ITS COMPOUNDS HAVE BEEN USED SINCE AT LEAST 4000 ┬├. ╙TIBNITE (ANTIMONY SULFIDE), FOR EXAMPLE, WAS USED AS AN EYEBROW PIGMENT. ╘HE CHEMICAL SYMBOL ╙B IS DERIVED FROM STIBIUM, THE ╠ATIN NAME FOR STIBNITE. ═ETALLIC ANTIMONY MELTS AT 630.5 DEG ├ AND BOILS AT 1,380 DEG ├; ITS DENSITY IS 6.69 G/ML. ╔TS ELECTRICAL CONDUCTIVITY IS ONLY 3.76% AS GREAT AS SILVER.
┴RGON
┴RGON IS A CHEMICAL ELEMENT--A MONATOMIC GAS--THE THIRD OF THE ╬OBLE GASES IN GROUP 0 OF THE PERIODIC TABLE. ╔TS SYMBOL IS ┴R; ITS ATOMIC NUMBER IS 18, AND ITS ATOMIC WEIGHT IS 39.948. ┴RGON IS THE MOST ABUNDANT OF THE INERT, OR SO-CALLED NOBLE, GASES IN THE ATMOSPHERE, BEING PRESENT TO THE EXTENT OF 0.94% BY VOLUME. ╬ATURALLY OCCURRING ARGON COMPRISES THREE ISOTOPES WITH PHYSICAL PROPERTIES THAT INCLUDE A MELTING POINT OF -189.2 DEG ├, A BOILING POINT OF -185.7 DEG ├, AND A GAS DENSITY OF 1.7837 G/L AT 0 DEG ├. ╘HE ELEMENT DOES NOT APPEAR TO FORM TRUE COMPOUNDS, ALTHOUGH IT IS KNOWN TO FORM A HYDRATE, AND SOME IONS HAVE BEEN DETECTED SPECTROSCOPICALLY.
┴RSENIC
[AHRS'-NIK] ┴RSENIC IS A METALLIC CHEMICAL ELEMENT. ╔TS SYMBOL IS ┴S, ITS ATOMIC NUMBER 33, AND ITS ATOMIC WEIGHT 74.9216. ┴RSENIC EXISTS IN THREE ALLOTROPIC MODIFICATIONS: THE YELLOW (REPRESENTED BY ╟REEK LOWER-CASE LETTER ALPHA); THE BLACK (REPRESENTED BY ╟REEK LOWER-CASE LETTER BETA); AND THE METALLIC, OR GRAY (REPRESENTED BY ╟REEK LOWER-CASE LETTER GAMMA). ╬ORMALLY ARSENIC IS FOUND IN ITS METALLIC FORM, WHICH IS THE MOST STABLE AND AT NORMAL PRESSURE DOES NOT MELT BUT SUBLIMES AT ABOUT 615 DEG ├. ╔T FORMS ALLOYS WITH OTHER METALS. ╘HE ALPHA AND BETA MODIFICATIONS HAVE NO METALLIC PROPERTIES. ┴RSENIC IS FAIRLY REACTIVE. ┴BOVE 400 DEG ├ IT BURNS WITH A BLUISH FLAME, FORMING ARSENIC TRIOXIDE. ╘HIS COMPOUND IS KNOWN AS WHITE ARSENIC AND IS USED AS A RAT POISON.
┴STATINE
[AS'-TUH-TEEN] ┴STATINE IS A RADIOACTIVE CHEMICAL ELEMENT, THE FIFTH AND FINAL OF THE HALOGEN ELEMENTS. ╔TS SYMBOL IS ┴T; ITS ATOMIC NUMBER 85; AND ITS ATOMIC WEIGHT 210 (STABLEST ISOTOPE). ╘HE NAME IS DERIVED FROM THE ╟REEK ASTATOS, MEANING "UNSTABLE." ┴STATINE IS ONE OF THE RAREST ELEMENTS IN NATURE, AND THE ┼ARTH'S CRUST IS ESTIMATED TO CONTAIN LESS THAN 30 G (1 OZ.) ╘WENTY ISOTOPES ARE KNOWN, OF WHICH ┴T-210 IS THE LONGEST-LIVED, WITH A HALF-LIFE OF 8.3 HOURS. ╘HE MELTING POINT OF ASTATINE IS 302 DEG ├, AND ITS BOILING POINT IS 337 DEG ├. ╙INCE IT IS SHORT-LIVED, ITS CHEMICAL PROPERTIES ARE DIFFICULT TO INVESTIGATE.
┬ARIUM
┬ARIUM IS A CHEMICAL ELEMENT--A SILVERY, SOFT METAL--AND IT IS THE FIFTH OF THE ┴LKALINE ┼ARTH METALS FORMING ╟ROUP ╔╔ IN THE PERIODIC TABLE. ╔TS SYMBOL IS ┬A; ITS ATOMIC NUMBER IS 56; AND ITS ATOMIC WEIGHT IS 137.34. ╘HE DENSITY OF BARIUM IS 3.75 G/CU CM AT 20 DEG ├; ITS MELTING POINT IS APPROXIMATELY 725 DEG ├, AND ITS BOILING POINT IS APPROXIMATELY 1,640 DEG ├. ╘HE NAME BARIUM IS DERIVED FROM THE ╟REEK BARUS, MEANING "HEAVY."
┬ERKELIUM
┬ERKELIUM IS A CHEMICAL ELEMENT, A METAL OF THE ┴CTINIDE SERIES IN ╟ROUP ╔╔╔┬ OF THE PERIODIC TABLE. ╔TS SYMBOL IS ┬K, ITS ATOMIC NUMBER 97, AND ITS WEIGHT 247 (STABLEST ISOTOPE). ┬ERKELIUM DOES NOT OCCUR NATURALLY. ╟LENN ╙EABORG, ╙. ╟. ╘HOMPSON, AND ┴. ╟HIORSO SYNTHESIZED (243)┬K IN 1949 BY BOMBARDING AMERICIUM 241 WITH HELIUM IONS IN A CYCLOTRON AT THE ╒NIVERSITY OF ├ALIFORNIA AT ┬ERKELEY; THE NEWLY DISCOVERED ELEMENT WAS NAMED IN HONOR OF THAT CITY. ╘HE KNOWN ISOTOPES, WHOSE MASS NUMBERS RANGE FROM 240 TO 251, ARE RADIOACTIVE; ┬K-247 IS THE STABLEST ISOTOPE, WITH A HALF-LIFE OF ABOUT 1,400 YEARS.
┬ERYLLIUM
┬ERYLLIUM IS A CHEMICAL ELEMENT, ONE OF THE ALKALINE-EARTH METALS IN ╟ROUP ╔╔┴ OF THE PERIODIC TABLE. ╔TS SYMBOL IS ┬E, ITS ATOMIC NUMBER 4, AND ITS ATOMIC WEIGHT 9.0122. ┴ STEEL-GRAY METAL, ITS PROPERTIES ARE SIMILAR TO THOSE OF ALUMINUM AND MAGNESIUM, EXCEPT THAT ITS MELTING POINT, ABOUT 1,278 DEG ├, IS HIGH FOR A LIGHT METAL. ├HEMICALLY, BERYLLIUM DIFFERS MARKEDLY FROM THE OTHER ALKALINE-EARTH METALS IN THAT IT FORMS COMPOUNDS THAT ARE MORE COVALENT THAN IONIC.
┬ISMUTH
[BIZ'-MUHTH] ╘HE CHEMICAL ELEMENT BISMUTH IS A SOFT, BRITTLE, HIGHLY LUSTROUS METAL BELONGING TO THE SAME GROUP IN THE PERIODIC TABLE AS ARSENIC. ╔TS SYMBOL IS ┬I; ITS ATOMIC NUMBER IS 83; ITS ATOMIC WEIGHT IS 208.9806. ╘HE AVERAGE ABUNDANCE OF BISMUTH IN THE ┼ARTH'S CRUST IS ABOUT 0.00002%. ┬ISMUTH METAL HAS A MELTING POINT OF 271 DEG ├ (520 DEG ╞) AND A BOILING POINT OF 1,560 DEG ├ (2,840 DEG ╞). ╧N FREEZING, MOLTEN BISMUTH EXPANDS 3.3% BY VOLUME, A PROPERTY SHARED BY ONLY ONE OTHER ELEMENT, GALLIUM. ┬ISMUTH FORMS COMPOUNDS IN THE +3 AND +5 OXIDATION STATES; THE +3 STATE IS THE MORE STABLE OF THE TWO.
┬ORON
[BOHR'-AHN] ┬ORON IS A METALLOID CHEMICAL ELEMENT WITH PROPERTIES INTERMEDIATE BETWEEN THOSE OF CARBON AND ALUMINUM. ╔TS CHEMICAL SYMBOL IS ┬, ATOMIC NUMBER 5, AND ATOMIC WEIGHT 10.811. ┬ORON IS RELATIVELY RARE. ╘HE LOW ELECTRICAL CONDUCTIVITY OF BORON INCREASES GR┼╠TLY AS ITS TEMPERATURE IS RAISED. ┬ORON HAS THREE VALENCE ELECTRONS AND FORMS COVALENT COMPOUNDS ALMOST EXCLUSIVELY. ╘HESE COMPOUNDS DO NOT HAVE A RARE GAS CONFIGURATION, SINCE THEY HAVE ONLY SIX ELECTRONS. ╘HE RARE GAS CONFIGURATION WITH EIGHT BONDING ELECTRONS CAN BE ATTAINED IN REACTIONS OF MOLECULES WITH FREE ELECTRON PAIRS.
┬ROMINE
[BROH'-MEEN] ╘HE CHEMICAL ELEMENT BROMINE IS A LIQUID WITH A POWERFUL, UNPLEASANT ODOR. ╔TS SYMBOL IS ┬R; ITS ATOMIC NUMBER 35; AND ITS ATOMIC WEIGHT 79.904. ╔N ITS ELEMENTAL STATE IT IS A DEEP-RED COLOR, SO DARK AS TO APPEAR ALMOST BLACK. ╔T IS A NONMETAL APPEARING ON THE PERIODIC CHART OF THE ELEMENTS AS A MEMBER OF FAMILY ╓╔╔A, THE ╚ALOGENS. ╘HE ┴CADEMIE ╞RANCAISE DID NOT ACCEPT THE PROPOSED NAME, AND INSTEAD BROMINE, MEANING "STENCH," OR "BAD ODOR," IS NOW USED.
├ADMIUM
╘HE CHEMICAL ELEMENT CADMIUM IS A RELATIVELY RARE, SOFT, SILVER-WHITE METAL CLOSELY RELATED TO ┌INC. ╔TS CHEMICAL SYMBOL IS ├D, ITS ATOMIC NUMBER IS 48, AND ITS ATOMIC WEIGHT IS 112.40. ┴BOUT 75% OF ALL CADMIUM PRODUCED IS USED FOR CADMIUM PLATING OF EASILY CORRODED METALS SUCH AS IRON AND STEEL. ┬ECAUSE OF ITS LOW MELTING POINT, CADMIUM IS USED IN SPECIAL ALLOYS SUCH AS ALUMINUM SOLDER (40% CADMIUM, 50% LEAD, 10% TIN); ╫OOD'S METAL (50% BISMUTH, 25% LEAD, 15% CADMIUM, 10% TIN), WHICH HAS A MELTING POINT OF 70 DEG ├; AND RELATED ALLOYS THAT ARE
├ALCIUM
╘HE CHEMICAL ELEMENT CALCIUM IS A MALLEABLE, LIGHT, SILVER-WHITE METAL, A MEMBER OF THE ┴LKALINE ┼ARTH ═ETAL GROUP. ╔TS SYMBOL IS ├A, ATOMIC NUMBER 20, AND ATOMIC WEIGHT 40.08. ├ALCIUM IS IMPORTANT IN THE BODY AS AN ELECTROLYTE AND AS THE BASIS OF BONE FORMATION. ├ALCIUM MELTS AT 839 ├ AND BOILS AT 1484 ├. ├ALCIUM. LIKE MOST OF THE ┴LKALINE ┼ARTH ═ETALS SHOWS A COMMON VALANCE CHARGE OF +2.
├ALIFORNIUM
├ALIFORNIUM IS A CHEMICAL ELEMENT, A RADIOACTIVE METAL OF THE ┴CTINIDE ╙ERIES. ╔TS SYMBOL IS ├F, ITS ATOMIC NUMBER 98, AND ITS ATOMIC WEIGHT 251 FOR THE STABLEST ISOTOPE. ├ALIFORNIUM DOES NOT OCCUR NATURALLY. ╘HE ELEMENT WAS FIRST SYNTHESIZED IN 1950 BY ╙. ╟. ╘HOMPSON, ╦. ╙TREET, ╩R., ┴. ╟HIORSO, AND ╟LENN ╘. ╙EABORG, WHO BOMBARDED A FEW MICROGRAMS OF CURIUM-242 WITH HELIUM IONS TO FORM THE MASS-245 ISOTOPE OF THE NEW ELEMENT. ╬AMED FOR THE ╒NIVERSITY OF ├ALIFORNIA AND FOR THE STATE, CALIFORNIUM HAS BEEN USED
EXTENSIVELY IN THE STUDY OF FISSION.
├ARBON
├ARBON IS A NONMETALLIC CHEMICAL ELEMENT FOUND WIDELY IN NATURE. ├ARBON IS FOUND BOTH IN NATIVE FORM AND IN COMPOUNDS WITH OTHER ELEMENTS, MAKING UP ABOUT 0.2% BY WEIGHT OF THE ┼ARTH'S CRUST. ╘HE ELEMENT IS FOUND IN ITS PUREST FORM AS DIAMOND AND GRAPHITE. ├ARBON (SYMBOL ├, ATOMIC NUMBER 6, ATOMIC WEIGHT 12.011) IS A MEMBER OF GROUP ╔╓┴ OF THE PERIODIC TABLE ALONG WITH SILICON, GERMANIUM, TIN, AND LEAD. ╔T IS THE LIGHTEST AND LEAST METALLIC OF THESE ELEMENTS. ╒NLIKE MANY OTHER GROUPS IN THE PERIODIC TABLE, THE GROUP ╔╓┴ ELEMENTS DIFFER GREATLY FROM EACH OTHER IN THEIR CHEMISTRY, WITH CARBON BEING THE LEAST REPRESENTATIVE IN ITS BEHAVIOR.
├ERIUM
[SIR'-EE-UHM] ├ERIUM IS A CHEMICAL ELEMENT, THE MOST ABUNDANT OF THE ╠ANTHANIDE ╙ERIES. ╔TS SYMBOL IS ├E, ATOMIC NUMBER 58, AND ATOMIC WEIGHT 140.12. ╔T OCCURS IN MANY MINERALS, ESPECIALLY MONAZITE AND BASTNAESITE. ╘HE ELEMENT WAS DISCOVERED IN 1803 BY ═. ╚. ╦LAPROTH AND INDEPENDENTLY BY ╩. ╩. ┬ERZELIUS AND ╫. ╚ISINGER. ╔T WAS NAMED AFTER ├ERES, AN ASTEROID.
├ESIUM
[SEE'-ZEE-UHM] ├ESIUM IS A CHEMICAL ELEMENT, A SOFT, SILVER-WHITE ┴LKALI ═ETAL. ╔TS SYMBOL IS ├S, ITS ATOMIC NUMBER 55, AND ITS ATOMIC WEIGHT 132.905. ╘HE ELEMENT WAS DISCOVERED BY ╥OBERT ┬UNSEN AND ╟USTAV ╦IRCHOFF IN 1860. ╘HE STABLE ISOTOPE ├S-133 OCCURS NATURALLY. ═ANY RADIOACTIVE ISOTOPES HAVE BEEN PRODUCED ARTIFICIALLY; ├S-137, WITH A HALF-LIFE OF 33 YEARS, IS USED AS A SOURCE OF GAMMA RADIATION. ├ESIUM REACTS VIOLENTLY WITH WATER, AND MAY IGNITE SPONTANEOUSLY ON EXPOSURE TO MOIST AIR.
├HLORINE
╘HE CHEMICAL ELEMENT CHLORINE IS A GREENISH YELLOW GAS WITH A SHARP, DISAGREEABLE ODOR. ╔T BELONGS TO THE ╚ALOGENS, A GROUP THAT INCLUDES THE ELEMENTS BROMINE, FLUORINE, IODINE, AND ASTATINE. ╔TS CHEMICAL SYMBOL IS ├L, ATOMIC NUMBER 17, AND ATOMIC WEIGHT 35.453. ├HLORINE IS ABOUT 2.5 TIMES AS DENSE AS AIR AND MODERATELY SOLUBLE IN WATER, FORMING A PALE YELLOWISH GREEN SOLUTION. ╘HE NAME "CHLORINE," FROM A ╟REEK WORD MEANING "GREENISH YELLOW." ├HLORINE CAN SUPPORT COMBUSTION. ├HLORINE FORMS FIVE DIFFERENT OXIDES: DICHLORINE MONOXIDE; CHLORINE MONOXIDE; CHLORINE DIOXIDE; CHLORINE HEXOXIDE; AND CHLORINE HEPTOXIDE.
├HROMIUM
╘HE CHEMICAL ELEMENT CHROMIUM IS A LUSTROUS METAL OF THE TRANSITION SERIES
. ╔TS CHEMICAL SYMBOL IS ├R, ATOMIC NUMER 24, AND ATOMIC WEIGHT 51.996. ├HROMIUM WAS DISCOVERED IN 1798 BY ╬. ╠. ╓AUQUELIN. ╔TS NAME IS DERIVED FROM THE ╟REEK WORD FOR COLOR, SINCE MOST CHROMIUM COMPOUNDS ARE BRIGHTLY COLORED. ├HROMIUM DOES NOT OCCUR FREE IN NATURE; IN BOUND FORM IT MAKES UP 0.1-0.3 PARTS PER MILLION OF THE ┼ARTH'S CRUST.
├OBALT
╘HE CHEMICAL ELEMENT COBALT IS A HARD SILVER METAL WITH A BLUISH SHEEN. ╔TS CHEMICAL SYMBOL IS ├O, ITS ATOMIC NUMBER IS 27, AND ITS ATOMIC WEIGHT IS 58.9332. ╘HE NAME COBALT, DERIVED FROM THE ╟ERMAN KOBOLD (A MALICIOUS UNDERGROUND GOBLIN OR DEMON), ORIGINATED IN THE 16TH CENTURY, WHEN ARSENIC-CONTAINING COBALT ORES WERE DUG UP IN SILVER MINES OF THE ╚ARZ ═OUNTAINS. ├HEMICALLY, COBALT RESEMBLES IRON AND NICKEL. ╔RON IS SITUATED TO ITS LEFT AND NICKEL TO ITS RIGHT IN THE ╨ERIODIC ╘ABLE. ╘HESE THREE METALS CONSTITUTE THE IRON GROUP. ╘HE MOST COMMON VALENCE OF COBALT IS +2; TRIVALENT COBALT SALTS ARE USUALLY STRONG OXIDIZING AGENTS, AND A VALENCE OF +4 OCCURS IN RARE
INSTANCES.
├OPPER
╘HE CHEMICAL ELEMENT COPPER IS A REDDISH METAL AT THE HEAD OF GROUP ╔┬ IN THE PERIODIC TABLE. ╔TS SYMBOL IS ├U; ATOMIC NUMBER, 29; AND ATOMIC WEIGHT, 63.546. ╘HE NAME IS DERIVED FROM THE ╠ATIN CUPRUM, "COPPER." ├OPPER MELTS AT 1,083.4 DEG ├, BOILS AT 2,567 DEG ├, AND HAS A DENSITY OF 8.96 AT 20 DEG ├. ╘HE ELEMENT HAS A HARDNESS OF 3, TAKES ON A BRIGHT METALLIC LUSTER, HAS A CUBIC CRYSTAL STRUCTURE, AND IS MALLEABLE, DUCTILE, AND A GOOD CONDUCTOR OF HEAT AND ELECTRICITY, SECOND ONLY TO SILVER IN ELECTRICAL CONDUCTIVITY. ├OPPER EXHIBITS OXIDATION STATES OF +2 (THE MOST COMMON, FORMING ├U(╔╔) COMPOUNDS), AND +1 (├U(╔), STABLE ONLY IN AQUEOUS SOLUTION IF PART OF A STABLE COMPLEX ION); A FEW COMPOUNDS OF COPPER(╔╔╔) ARE ALSO KNOWN.
├URIUM
[KUER'-EE-UHM] ├URIUM IS A CHEMICAL ELEMENT, A RADIOACTIVE METAL OF THE ┴CTINIDE ╙ERIES, IN ╟ROUP ╔╔╔┬ OF THE PERIODIC TABLE. ╔TS SYMBOL IS ├M, ITS ATOMIC NUMBER 96, AND ITS ATOMIC WEIGHT 247 (STABLEST ISOTOPE). ├URIUM DOES NOT OCCUR NATURALLY. ╔T WAS NAMED AFTER THE ╞RENCH SCIENTISTS ═ARIE AND ╨IERRE ├URIE. ├URIUM IS A SILVERY, HARD, BRITTLE METAL. ├M-244, WITH A HALF-LIFE OF ABOUT 18 YEARS, CAN BE USED AS A HEAT SOURCE FOR COMPACT THERMOELECTRIC POWER GENERATION.
─YSPROSIUM
[DIS-PROH'-ZEE-UHM] ╘HE CHEMICAL ELEMENT DYSPROSIUM IS A SILVER GRAY RARE-EARTH METAL. ╔TS SYMBOL IS ─Y, ATOMIC NUMBER 66, AND ATOMIC WEIGHT 162.50. ╘HE ELEMENT WAS IDENTIFIED IN 1886 BY ╠ECOQ DE ┬OISBAUDRAN BUT WAS NOT ISOLATED UNTIL 1950. ╔TS NAME IS DERIVED FROM THE ╟REEK WORD DYSPROSITOS, MEANING "DIFFICULTY OF ACCESS." ╙EVEN ISOTOPES OCCUR NATURALLY. ─YPROSIUM HAS A VALENCE OF +3. ╔TS OXIDE IS USED IN CONTROL DEVICES FOR NUCLEAR REACTORS BECAUSE THE METAL HAS A HIGH NEUTRON-ABSORBING CAPABILITY, AND IN CRYOGENIC MAGNETIC COOLING DEVICES BECAUSE IT IS ONE OF THE MOST PARAMAGNETIC SUBSTANCES KNOWN.
┼INSTEINIUM
[YN-STYN'-EE-UHM] ╘HE CHEMICAL ELEMENT EINSTEINIUM IS A RADIOACTIVE METAL OF THE ┴CTINIDE ╙ERIES AND A TRANSURANIUM
ELEMENT. ╔TS SYMBOL IS ┼S, ITS ATOMIC NUMBER IS 99, AND THE ATOMIC WEIGHT OF ITS MOST STABLE ISOTOPE IS 254. ┼INSTEINIUM DOES NOT OCCUR IN NATURE. ╔T WAS FIRST DISCOVERED IN THE DEBRIS FROM THE "═IKE" THERMONUCLEAR EXPLOSION IN THE ╙OUTH ╨ACIFIC IN 1952. ┼INSTEINIUM WAS NAMED IN HONOR OF ┴LBERT ┼INSTEIN. ┴LL KNOWN ISOTOPES OF EINSTEINIUM ARE RADIOACTIVE, WITH HALF-LIVES RANGING FROM A FEW SECONDS TO ABOUT 1 YEAR.
┼RBIUM
[UR'-BEE-UHM] ┼RBIUM IS A CHEMICAL ELEMENT, A SHINY METAL OF THE ╠ANTHANIDE ╙ERIES. ╔TS SYMBOL IS ┼R, ITS ATOMIC NUMBER 68, AND ITS ATOMIC WEIGHT 167.2. ╘HE SIX NATURALLY OCCURRING ERBIUM ISOTOPES--┼R-162, ┼R-164, ┼R-166, ┼R-167, ┼R-168, AND ┼R-170--ARE NOT RADIOACTIVE. ╘HE NUMEROUS SYNTHETIC ISOTOPES OF ERBIUM ARE ALL RADIOACTIVE. ┼RBIUM WAS FIRST IDENTIFIED IN NATURE BY ├. ╟. ═OSANDER IN 1842. ┬ECAUSE OF ITS CAPACITY TO ABSORB NEUTRONS, ERBIUM IS WIDELY USED IN MANUFACTURING NUCLEAR CONTROL RODS. ╔T IS ALSO USED IN MAGNETIC ALLOYS.
┼UROPIUM
[YUR-OHP'-EE-UHM] ┼UROPIUM IS A CHEMICAL ELEMENT, A METAL OF THE ╠ANTHANIDE ╙ERIES. ╔TS SYMBOL IS ┼U; ITS ATOMIC NUMBER IS 63; AND ITS ATOMIC WEIGHT IS 151.96. ╘WO ISOTOPES OF EUROPIUM OCCUR NATURALLY, ┼U-151 AND ┼U-153; BOTH ARE STABLE. ═ANY RADIOACTIVE, ARTIFICIAL ISOTOPES OF EUROPIUM HAVE BEEN CREATED. ╘HE EXISTENCE OF EUROPIUM WAS FIRST POSTULATED BY ╙IR ╫ILLIAM ├ROOKES IN 1889. ╔N 1896, ┼. ┴. ─EMARCAY DISCOVERED ELEMENT 63 AND NAMED IT FOR ┼UROPE. ┼UROPIUM, A SOFT METAL, IS THE MOST REACTIVE OF THE LANTHANIDES, AND MANY OF ITS PROPERTIES ARE MORE LIKE THOSE OF CALCIUM, STRONTIUM, AND BARIUM. ┼UROPIUM OXIDE IS USED AS THE RED PHOSPHOR IN CATHODE-RAY TUBES FOR
COLOR TELEVISION RECEIVERS.
╞ERMIUM
[FUR'-MEE-UHM] ╘HE CHEMICAL ELEMENT FERMIUM, NAMED FOR ┼NRICO ╞ERMI, IS A METAL OF THE ┴CTINIDE ╙ERIES. ╔TS SYMBOL IS ╞M, ITS ATOMIC NUMBER IS 100, AND THE ATOMIC WEIGHT OF ITS STABLEST ISOTOPE IS 257. ╠IKE OTHER ╘RANSURANIUM ┼LEMENTS, FERMIUM DOES NOT OCCUR NATURALLY. ╔T AND EINSTEINIUM WERE FIRST PRODUCED IN A THERMONUCLEAR EXPLOSION IN THE ╙OUTH ╨ACIFIC IN 1952, AND IDENTIFIED BY THE ┴MERICAN CHEMIST ╟LENN ╙EABORG AND HIS COLLABORATORS. ┴LL KNOWN ISOTOPES OF FERMIUM ARE RADIOACTIVE, THEIR HALF-LIVES RANGING FROM A FEW MILLISECONDS TO ABOUT 100 DAYS. ╘HE TOTAL AMOUNT OF FERMIUM THAT HAS BEEN SYNTHESIZED IS LESS THAN ONE-MILLIONTH OF A GRAM.
╞LUORINE
╞LUORINE IS A PALE YELLOW, POISONOUS, HIGHLY CORROSIVE GAS. ╔T IS THE LIGHTEST MEMBER OF THE ╚ALOGENS AND THE MOST REACTIVE OF ALL ELEMENTS. ╔TS SYMBOL IS ╞, ITS ATOMIC WEIGHT IS 18.99840, AND ITS ATOMIC NUMBER IS 9. ╘HE NAME FLUORINE IS DERIVED FROM THE MINERAL FLUORSPAR, WHICH, IN TURN, IS DERIVED FROM THE ╠ATIN FLUO, "FLOW." ╞LUORINE EXISTS AS A DIATOMIC GAS. ╚IGHLY TOXIC, IT HAS A CHARACTERISTIC PUNGENT ODOR THAT CAN BE DETECTED BEFORE HAZARDOUS CONCENTRATIONS BUILD
UP. ╞LUORINE BOILS AT-188 DEG ├ (- 370
DEG ╞) AND ITS MELTING POINT IS - 219
DEG ├ (- 426 DEG ╞). ╧NLY ONE STABLE ISOTOPE OF FLUORINE OCCURS. ╘HE FLUORINE ATOM HAS SEVEN ELECTRONS IN ITS OUTER SHELL AND REQUIRES AN ADDITIONAL ELECTRON FOR MAXIMUM STABILITY.
╞RANCIUM
[FRAN'-SEE-UHM] ╞RANCIUM, OR EKA-CESIUM, IS A RADIOACTIVE CHEMICAL ELEMENT, ONE OF THE ALKALI METALS. ╔TS SYMBOL IS ╞R AND ITS ATOMIC NUMBER 87. ╘HE ATOMIC WEIGHTS OF ╞R ISOTOPES RANGE WIDELY; THE STABLEST ISOTOPE IS CALLED ACTINIUM-╦, WITH A HALF-LIFE OF ABOUT 21 MINUTES. ═ENDELEYEV POSTULATED THE EXISTENCE OF ELEMENT 87, BUT FRANCIUM WAS NOT IDENTIFIED UNTIL 1939, WHEN ═ARGUERITE ╨EREY DISCOVERED IT AS A PRODUCT OF ACTINIUM DECAY. ╞RANCIUM OCCURS IN SUCH MINUTE AMOUNTS IN NATURE THAT IT CANNOT BE ISOLATED.
╟ADOLINIUM
[GAD-UH-LIN'-EE-UHM] ╘HE CHEMICAL ELEMENT GADOLINIUM IS A LUSTROUS, MAGNETIC METAL OF THE RARE EARTH ╠ANTHANIDE ╙ERIES, GROUP ╔╔╔┬ OF THE PERIODIC TABLE. ╔TS SYMBOL IS ╟D, ITS ATOMIC NUMBER 64, ITS ATOMIC WEIGHT 157.25, AND ITS VALENCE +3. ╔T IS OFTEN FOUND IN ASSOCIATION WITH OTHER RARE EARTH ELEMENTS. ╟ADOLINIUM WAS NAMED FOR THE ╞INNISH CHEMIST ╩OHAN ╟ADOLIN. ╘HERE ARE SEVEN NATURALLY OCCURRING ISOTOPES. ┴T LEAST ONE--152-╟D--IS RADIOACTIVE, WITH A HALF-LIFE OF 1.1 ╪ 10 TO THE 14TH POWER YEARS. ╔T IS USED IN NOISE FILTERS, IN PHOSPHORS FOR COLOR TELEVISIONS, AND, IN SMALL AMOUNTS, TO INCREASE THE TENSILE STRENGTH AND ELECTRICAL CONDUCTIVITY OF SOME OTHER METALS.
╟ALLIUM
[GAL'-EE-UHM] ╘HE CHEMICAL ELEMENT GALLIUM IS A BLUISH METAL OF GROUP ╔╔╔┴ IN THE PERIODIC TABLE. ╔TS CHEMICAL SYMBOL IS ╟A, ATOMIC NUMBER 31, AND ATOMIC WEIGHT 69.72. ╟ALLIUM IS A RELATIVELY RARE METAL THAT IS BECOMING INCREASINGLY IMPORTANT IN THE MANUFACTURE OF SEMICONDUCTORS. ╟ALLIUM IS NAMED AFTER ╟ALLIA, THE ╠ATIN NAME FOR ╞RANCE. ╠ATER THE SAME YEAR, ─MITRY ═ENDELEYEV SHOWED THAT GALLIUM WAS THE MISSING GROUP ╔╔╔┴ ELEMENT BELOW ALUMINUM AND ABOVE INDIUM PREDICTED IN HIS THEORY OF CHEMICAL PERIODICITY. ╘HE PURE METAL HAS A SLIGHT BLUISH LUSTER RESEMBLING THAT OF ZINC. ╔TS MELTING POINT (29.78 DEG ├) IS UNUSUALLY LOW, AND THE BOILING POINT ABOUT 2,250 DEG ├. ═OLTEN GALLIUM EXPANDS IN VOLUME BY 3.2% ON FREEZING; AMONG ALL THE OTHER ELEMENTS ONLY BISMUTH SHARES THIS PROPERTY.
╟ERMANIUM
[JUR-MAYN'-EE-UHM] ╘HE CHEMICAL ELEMENT GERMANIUM, IS SEMIMETAL OF GROUP ╔╓┴ IN THE PERIODIC TABLE. ╔TS SYMBOL IS ╟E, ATOMIC NUMBER 32, AND ATOMIC WEIGHT 72.59. ╘HE ╟ERMAN CHEMIST ├LEMENS ┴. ╫INKLER FIRST ISOLATED THE ELEMENT IN 1886 FROM THE MINERAL ARGYRODITE, A MIXED SULFIDE OF SILVER AND GERMANIUM, AND NAMED IT AFTER HIS HOMELAND. ╟ERMANIUM IS WIDELY DISTRIBUTED IN THE ┼ARTH'S CRUST, WITH AN AVERAGE ABUNDANCE OF ABOUT 7 GRAMS PER METRIC TON. ╘HE ELEMENT IS USUALLY FOUND AS A MINOR COMPONENT IN SULFIDE ORES OF COPPER, ZINC, TIN, LEAD, AND ANTIMONY. ╟ERMANIUM HAS A BRITTLE METALLIC APPEARANCE, A MELTING POINT OF 937.4 DEG ├, AND A BOILING POINT OF 2,830 DEG ├. ╔T CRYSTALLIZES IN A CUBIC STRUCTURE SIMILAR TO DIAMOND BUT HAS A HARDNESS OF 6 ON THE ═OHS SCALE. ╔T FORMS COMPOUNDS IN THE +2 AND +4 OXIDATION STATES.
╟OLD
╘HE CHEMICAL ELEMENT GOLD, ATOMIC NUMBER 79, SYMBOL ┴U (FROM THE ╠ATIN AURUM), IS A SOFT, LUSTROUS YELLOW, MALLEABLE METAL. ╔T IS ONE OF THE TRANSITION METALS AND ITS ATOMIC WEIGHT IS 196.967. ╟OLD IS THE MOST MALLEABLE OF ALL METALS. ╔T CAN BE BEATEN INTO SHEETS APPROACHING A SINGLE ATOM OF THICKNESS, SO THIN AS TO TRANSMIT LIGHT.
╚AFNIUM
[HAF'-NEE-UHM] ╘HE CHEMICAL ELEMENT HAFNIUM IS A LUSTROUS, DUCTILE, SILVERY METAL OF GROUP ╔╓┬ OF THE PERIODIC TABLE. ╔TS SYMBOL IS ╚F, ITS ATOMIC NUMBER IS 72, AND ITS ATOMIC WEIGHT IS 178.49. ╔TS VALENCE, OR OXIDATION NUMBER, IS MOST OFTEN +4. ╚AFNIUM IS ALWAYS FOUND IN COMBINATION WITH ZIRCONIUM. ╔T WAS IDENTIFIED IN ├OPENHAGEN IN 1923 BY THE ─ANISH PHYSICIST ─IRK ├OSTER AND THE ╚UNGARIAN CHEMIST ╟EORGE DE ╚EVESY. ╔TS NAME COMES FROM ╚AFNIA, THE ╠ATIN NAME FOR ├OPENHAGEN. ╚AFNIUM ABSORBS NEUTRONS AND IS USED IN THE CONTROL RODS OF SOME NUCLEAR REACTORS. ╔T IS ALSO USED IN LIGHT-BULB FILAMENTS AND AS A STRENGTHENING AGENT IN SOME ALLOYS.
╚ELIUM
[HEE'-LEE-UHM] ╘HE CHEMICAL ELEMENT HELIUM IS THE FIRST MEMBER OF THE NOBLE GASES, GROUP ╧ OF THE PERIODIC TABLE. ╔T IS A COLORLESS, NONTOXIC GAS; ITS SYMBOL IS ╚E, ATOMIC NUMBER 2, AND ATOMIC WEIGHT 4.00260. ╔TS NAME IS DERIVED FROM THE ╟REEK WORD HELIOS, MEANING "╙UN." ╘HE ELEMENT WAS FIRST ISOLATED FROM THE URANIUM MINERAL CLEVITE BY ╙IR ╫ILLIAM ╥AMSAY IN 1895 AND INDEPENDENTLY ABOUT THE SAME TIME BY ╨ER ╘EADOR ├LEVE AND ╬ILS ┴. ╠ANGLET IN╙WEDEN. ╘HE BOILING POINT OF HELIUM IS -268.93 DEG ├ (4.22 ╦). ╚ELIUM CANNOT BE SOLIDIFIED AT ATMOSPHERIC PRESSURE, EVEN AT ABSOLUTE ZERO. ┴T A PRESSURE OF 26 ATMOSPHERES, HELIUM BECOMES SOLID AT -272.2 ├. ╚ELIUM HAS THE LOWEST MELTING POINT OF ANY ELEMENT.
╚OLMIUM
[HOHL'-MEE-UHM] ╚OLMIUM IS A SILVERY, SOFT METAL OF THE RARE EARTHS, OR ╠ANTHANIDE ╙ERIES OF CHEMICAL ELEMENTS. ╔TS SYMBOL IS ╚O, ITS ATOMIC NUMBER 67, ITS ATOMIC WEIGHT 164.93, AND ITS GROUP ╔╔╔┬. ╘HE ONLY NATURALLY OCCURRING ISOTOPE, ╚O-165, IS STABLE. ╚OLMIUM FORMS SALTS WITH OXYGEN, CHLORINE, BROMINE, AND IODINE. ╔T WAS DISCOVERED IN 1878 BY ╩. ╠. ╙ORET AND ═. ─ELAFONTAINE AND INDEPENDENTLY BY ╨ER ╘EODOR ├LEVE (1879), WHO NAMED IT FOR THE CITY OF ╙TOCKHOLM.
╚YDROGEN
[HY'-DRUH-JEN] ╘HE CHEMICAL ELEMENT HYDROGEN IS AN INVISIBLE, FLAMMABLE GAS. ╔TS SYMBOL IS ╚, AND ITS ATOMIC NUMBER 1. ╘HE ATOMIC WEIGHT OF NATURAL HYDROGEN, WHICH CONTAINS TRACE AMOUNTS OF DEUTERIUM, IS 1.00797; THE ATOMIC WEIGHT OF THE PURE ISOTOPE IS 1.007825. ╚YDROGEN IS THE FIRST ELEMENT IN THE PERIODIC TABLE AND HAS THE SIMPLEST ATOMIC STRUCTURE OF ALL THE ELEMENTS; ITS NUCLEUS CONSISTS OF A SINGLE PROTON AND ONE OUTER ELECTRON. ┴LTHOUGH FORMALLY PLACED AT THE HEAD OF ╟ROUP ╔┴ OF THE PERIODIC TABLE, THE ALKALI METALS, HYDROGEN IS NOT A TRUE MEMBER OF THIS FAMILY OF ELEMENTS BUT IS TREATED AS AN INDEPENDENT ELEMENT. ╘HE NAME HYDROGEN, DERIVED FROM THE ╟REEK HYDRO, "WATER," AND GENES, "FORMING," WAS SUGGESTED BY ╠AVOISIER IN 1781.
╔NDIUM
[IN'-DEE-UHM] ╔NDIUM IS A RELATIVELY UNCOMMON METALLIC ELEMENT USED IN ENGINE-BEARING COATINGS, LOW-MELTING ALLOYS, AND SOLID-STATE ELECTRONICS. ╔TS CHEMICAL SYMBOL IS ╔N, ATOMIC NUMBER 49, AND ATOMIC WEIGHT 114.82. ╔T BELONGS TO GROUP ╔╔╔┴ IN THE PERIODIC TABLE, ALONG WITH BORON, ALUMINUM, GALLIUM, AND THALLIUM. ╘HE NAME IS DERIVED FROM THE INTENSE INDIGO BLUE COLOR THAT INDIUM SALTS IMPART TO FLAMES. ╨URE INDIUM IS A HIGHLY LUSTROUS, SILVER WHITE METAL (M.P. 156.17 DEG ├, B.P. 2,070 DEG ├, DENSITY 7.31 G/ML) AND IS SOFT AND EASILY DEFORMED UNDER PRESSURE. ╘HE METAL IS A WEAK REDUCING AGENT COMPARABLE TO COPPER. ╔NDIUM FORMS SALTS IN THE +1 AND +3 OXIDATION STATES.
╔ODINE
[Y'-UH-DINE] ╔ODINE, ATOMIC NUMBER 53, SYMBOL ╔, IS A SOLID NONMETALLIC ELEMENT OF THE ╚ALOGEN FAMILY, A GROUP THAT INCLUDES THE ELEMENTS FLUORINE, CHLORINE, AND BROMINE. ┴T ROOM TEMPERATURE IODINE IS A LUSTROUS, BLUE-BLACK, CRYSTALLINE SOLID OF ATOMIC WEIGHT 126.9045. ╔ODINE IS THE LEAST WATER-SOLUBLE HALOGEN, BUT ITS SOLUBILITY IS APPRECIABLY INCREASED IN AQUEOUS SOLUTIONS OF SODIUM IODIDE, DUE TO THE FORMATION OF POLYIODIDE COMPLEX IONS. ╔T DISSOLVES READILY IN ALCOHOL, CHLOROFORM, CARBON TETRACHLORIDE, AND BENZENE.
╔RIDIUM
[IR-ID'-EE-UHM] ╔RIDIUM IS A DENSE, BRITTLE, HARD, SILVER-WHITE PRECIOUS METAL. ┴ CHEMICAL ELEMENT, ITS SYMBOL IS ╔R, ATOMIC NUMBER 77, AND ATOMIC WEIGHT 192.22. ╘HE DISCOVERY OF IRIDIUM WAS ANNOUNCED IN 1804 BY ╙MITHSON ╘ENNANT, WHO NAMED THE METAL FROM THE ╠ATIN IRIS, MEANING "RAINBOW." ╔RIDIUM IS NOT FOUND IN NATURE IN PURE FORM BUT AS OSMIRIDIUM, AN ALLOY WITH OSMIUM AND PLATINUM. ═ANY RADIOACTIVE ISOTOPES OF IRIDIUM HAVE BEEN CREATED IN THE LABORATORY. ╘HE PURE METAL CANNOT BE DISSOLVED BY MOST ACIDS, INCLUDING AQUA REGIA. ╔RIDIUM IS USED IN PLATINUM ALLOYS FOR JEWELRY AND SURGICAL PINS; BECAUSE OF ITS RESISTANCE TO CORROSION, IT IS USED IN AIRCRAFT SPARK PLUGS.
╔RON
[Y'-URN] ╔RON, A SILVERY WHITE SOLID METAL, APPEARS IN ╟ROUP ╓╔╔╔ OF THE PERIODIC TABLE AS A ╘╥┴╬╙╔╘╔╧╬ ┼╠┼═┼╬╘. ╔TS ATOMIC NUMBER IS 26, AND ITS ATOMIC WEIGHT IS 55.847. ╔TS CHEMICAL SYMBOL, ╞E, IS DERIVED FROM FERRUM, THE ╠ATIN WORD FOR IRON. ╔RON IS NOTABLE AMONG THE ELEMENTS IN THE ABUNDANCE OF ITS ORES AND THE VAST NUMBER OF USEFUL ALLOYS THAT CAN BE FORMULATED WITH IRON AS THE MAJOR CONSTITUENT. ╔RON IS ALSO BIOLOGICALLY IMPORTANT; IT IS THE CENTRAL ATOM IN HEME, THE OXYGEN-CARRYING PORTION OF HEMAGLOBIN FOUND IN BLOOD.
╦RYPTON
[KRIP'-TAHN] ╘HE CHEMICAL ELEMENT KRYPTON IS THE FOURTH MEMBER OF THE NOBLE GASES, GROUP ╧ OF THE PERIODIC TABLE. ╘HE WORD KRYPTON IS DERIVED FROM THE ╟REEK KRYPTOS, MEANING "HIDDEN." ╦RYPTON'S SYMBOL IS ╦R, ITS ATOMIC NUMBER 36, AND ATOMIC WEIGHT 83.80. ╦RYPTON IS A MONATOMIC GAS. ╬ATURALLY OCCURRING KRYPTON IS COMPOSED OF SIX STABLE ISOTOPES. ╦RYPTON HAS A MELTING POINT OF -156.6 DEG ├, A BOILING POINT OF -152.30 DEG ├, AND A GES DENSITY OF 3.733 G/L AT 0 DEG ├. ╘HE ELEMENT WAS ORIGINALLY BELIEVED TO BE TRULY INERT, BUT A FEW COMPOUNDS SUCH AS KRYPTON DIFLUORIDE, A HYDRATE, AND CLATHRATES HAVE SINCE BEEN SYNTHESIZED.
╠ANTHANUM
[LAN'-THUH-NUHM] ╠ANTHANUM IS A CHEMICAL ELEMENT, A WHITE, MALLEABLE METAL, AND THE FIRST OF THE RERE EARTHS. ╔TS SYMBOL IS ╠A, ITS ATOMIC NUMBER 57, AND ITS ATOMIC WEIGHT 138.9 ╠ENTHANUM WITH MASS 138 IS RADIOACTIVE, WITH A HALF-LIFE OF 1.12 ╪ 100 BILLION YEARS. ╠ANTHANUM IS FOUND WITH OTHER LANTHANIDES IN MONAZITE, BASTNAESITE, AND OTHER MINERALS. ╔T WAS DISCOVERED IN 1839 BY ╙WEDISH CHEMIST ├ARL ╟. ═OSANDER. ╙CIENTISTS HAVE CREATED MANY RADIOACTIVE ISOTOPES OF LANTHANUM. ┬ECAUSE LANTHANUM INCREASES THE REFRACTIVE INDEX OF GLASS, IT IS USED IN MANUFACTURING HIGH-QUALITY LENSES. ╠ANTHANUM IS ALSO USED AS A REAGENT, AS A PHOSPHOR IN FLUORESCENT LAMPS, AND AS A CATALYST FOR CRACKING CRUDE PETROLEUM (ITS LARGEST USE).
╠AWRENCIUM
[LUH-RENS'-EE-UHM] ╠AWRENCIUM IS A SYNTHETIC RADIOACTIVE METAL, THE LAST MEMBER OF THE ┴CTINIDE ╙ERIES. ╔TS SYMBOL IS ╠R (ORIGINALLY ╠W); ITS ATOMIC NUMBER, 103; AND ITS ATOMIC WEIGHT, 260 (LONGEST-LIVED ISOTOPE). ╠AWRENCIUM DOES NOT OCCUR NATURALLY; IT WAS FIRST SYNTHESIZED AT THE ╥ADIATION ╠ABORATORY IN ┬ERKELEY, ├ALIF., IN 1961. ┬Y BOMBARDING A MIXTURE OF CALIFORNIUM ISOTOPES WITH BORON-LL IONS, ┴LBERT ╟HIORSO, ╘. ╙MKKELAND, ┴. ┼. ╠ARSH, AND ╥. ═. ╠ATIMER CREATED LAWRENCIUM WITH MASS 258, WITH A HALF-LIFE OF 4.2 SECONDS. ╘HE ELEMENT WAS NAMED FOR ┼RNEST ╠AWRENCE, THE INVENTOR OF THE CYCLOTRON. ╧THER LAWRENCIUM ISOTOPES HAVE BEEN CREATED BY BOMBARDING OTHER ╘RANSURANIUM ┼LEMENTS WITH HEAVY IONS.
╠EAD
╠EAD IS A LUSTROUS, SILVERY METAL THAT TARNISHES IN THE PRESENCE OF AIR AND BECOMES A DULL BLUISH GRAY. ╙OFT AND MALLEABLE, IT HAS A LOW MELTING POINT (327 DEG ├). ╔TS CHEMICAL SYMBOL, ╨B, IS DERIVED FROM PLUMBUM, THE ╠ATIN WORD FOR WATERWORKS, BECAUSE OF LEAD'S EXTENSIVE USE IN ANCIENT WATER PIPES. ╔TS ATOMIC NUMBER IS 82; ITS ATOMIC WEIGHT IS 207.19.
╠ITHIUM
╠ITHIUM IS A CHEMICAL ELEMENT OF THE ALKALI METALS, GROUP ╔┴ IN THE PERIODIC TABLE. ╔TS CHEMICAL SYMBOL IS ╠I, ATOMIC NUMBER 3, AND ATOMIC WEIGHT 6.941, WHICH IS THE LOWEST OF ALL METALS. ┴ SOFT, SILVERY-WHITE METAL, LITHIUM QUICKLY BECOMES COVERED WITH A GRAY OXIDATION LAYER WHEN IT IS EXPOSED TO AIR. ┴LTHOUGH A HIGHLY REACTIVE ELEMENT, LITHIUM IS LESS ACTIVE THAN THE OTHER ALKALI METALS. ╠IKE THE OTHERS, IT EASILY YIELDS AN ELECTRON, FORMING MONOVALENT POSITIVE IONS.
╠UTETIUM
[LOO-TEE'-SHEE-UHM] ╠UTETIUM IS A CHEMICAL ELEMENT, A SILVERY WHITE METAL OF THE ╠ANTHANIDE ╙ERIES. ╔TS SYMBOL IS ╠U, ITS ATOMIC NUMBER 71, AND ITS ATOMIC WEIGHT 174.97. ╠UTETIUM WITH MASS 176 IS REDIOACTIVE, WITH A HALF-LIFE OF 2.2 ╪ 10 BILLION YEARS. ╠UTETIUM WAS DISCOVERED IN 1907 BY ╟EORGES ╒RBAIN, WHO CALLED IT ╠UTETIA AFTER THE ANCIENT ╥OMAN NAME FOR ╨ARIS.
═AGNESIUM
═AGNESIUM IS A SILVERY WHITE METALLIC ELEMENT OF THE ┴LKALINE ┼ARTH ═ETAL GROUP, WHICH LIES IN GROUP ╔╔┴ OF THE PERIODIC TABLE. ╔TS CHEMICAL SYMBOL IS ═G, ATOMIC NUMBER 12, AND ATOMIC WEIGHT 24.312. ╔N 1808, ╙IR ╚UMPHREY ─AVY ANNOUNCED THAT HE HAD ISOLATED A NEW ELEMENT, MAGNESIUM, FROM THE HITHERTO UNKNOWN MAGNESIUM OXIDE, WHICH HE DISCOVERED. ┴NTOINE ┬USSY, WHO IS CREDITED WITH DISCOVERY OF THE METAL, ISOLATED LARGER AND PURER AMOUNTS IN 1828.
═ANGANESE
[MANG'-GUH-NEEZ] ╘HE CHEMICAL ELEMENT MANGANESE IS A SILVER GRAY METAL OF THE ╘RANSITION ┼LEMENTS. ╔TS CHEMICAL SYMBOL IS ═N, ITS ATOMIC NUMBER IS 25, AND ITS ATOMIC WEIGHT IS 54.938. ═ANGANESE WAS FIRST RECOGNIZED AS AN ELEMENT IN 1774 BY THE ╙WEDISH CHEMIST ├ARL ╫. ╙CHEELE AND ISOLATED IN THE SAME YEAR BY HIS COWORKER, ╩OHAN ╟. ╟AHN.
═ENDELEVIUM
[MEN-DUH-LAY'-VEE-UHM] ═ENDELEVIUM IS A RADIOACTIVE CHEMICAL ELEMENT OF THE ┴CTINIDE ╙ERIES. ╔TS SYMBOL IS ═D (ORIGINALLY ═V), ITS ATOMIC NUMBER 101, AND ITS ATOMIC WEIGHT 258 (STABLEST ISOTOPE). ═ENDELEVIUM WAS FIRST SYNTHESIZED IN 1955 BY ┴. ╟HIORSO, ┬. ╟. ╚ARVEY, ╟. ╥. ├HOPPIN, ╙. ╟. ╘HOMPSON, AND ╟LENN ╘. ╙EABORG, WHO BOMBARDED EINSTEINIUM-253 WITH HELIUM IONS. ╘HE ELEMENT WAS NAMED IN HONOR OF ─MITRY ═ENDELEYEV, THE DISCOVERER OF THE PERIODIC SYSTEM. ╘HE CREATION OF MENDELEVIUM WAS THE BASIS FOR THE DISCOVERY OF ALL THE CHEMICAL ELEMENTS WITH ATOMIC NUMBERS OVER 101.
