A Short History of Nearly Everything-第20章

按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！



fortunately　more　sober　types　were　at　work　elsewhere。　in　1808；　a　dour　quaker　named　johndalton　became　the　first　person　to　intimate　the　nature　of　an　atom　（progress　that　will　bediscussed　more　pletely　a　little　further　on）；　and　in　1811　an　italian　with　the　splendidlyoperatic　name　of　lorenzo　romano　amadeo　carlo　avogadro；　count　of　quarequa　and　cerreto；made　a　discovery　that　would　prove　highly　significant　in　the　long　term—namely；　that　twoequal　volumes　of　gases　of　any　type；　if　kept　at　the　same　pressure　and　temperature；　will　containidentical　numbers　of　molecules。

two　things　were　notable　about　avogadro’s　principle；　as　it　became　known。　first；　itprovided　a　basis　for　more　accurately　measuring　the　size　and　weight　of　atoms。　usingavogadro’s　mathematics；　chemists　were　eventually　able　to　work　out；　for　instance；　that　atypical　atom　had　a　diameter　of　0。00000008　centimeters；　which　is　very　little　indeed。　andsecond；　almost　no　one　knew　about　avogadro’s　appealingly　simple　principle　for　almost　fiftyyears。

2partly　this　was　because　avogadro　himself　was　a　retiring　fellow—he　worked　alone；corresponded　very　little　with　fellow　scientists；　published　few　papers；　and　attended　nomeetings—but　also　it　was　because　there　were　no　meetings　to　attend　and　few　chemicaljournals　in　which　to　publish。　this　is　a　fairly　extraordinary　fact。　the　industrial　revolution　was1the　confusion　over　the　aluminum/aluminium　spelling　arose　b　cause　of　some　uncharacteristic　indecisiveness　ondavys　part。　when　he　first　isolated　the　element　in　1808；　he　called　it　alumium。　for　son　reason　he　thought　better　ofthat　and　changed　it　to　aluminum　four　years　later。　americans　dutifully　adopted　the　new　term；　but　mai　britishusers　disliked　aluminum；　pointing　out　that　it　disrupted　the　…ium　pattern　established　by　sodium；　calcium；　andstrontium；　so　they　added　a　vowel　and　syllable。

2the　principle　led　to　the　much　later　adoption　of　avogadros　number；　a　basic　unit　of　measure　in　chemistry；　whichwas　named　for　avogadro　long　after　his　death。　it　is　the　number　of　molecules　found　in　2。016　grams　of　hydrogengas　（or　an　equal　volume　of　any　other　gas）。　its　value　is　placed　at　6。0221367　x　1023；　which　is　an　enormously　largenumber。　chemistry　students　have　long　amused　themselves　by　puting　just　how　large　a　number　it　is；　so　i　canreport　that　it　is　equivalent　to　the　number　of　popcorn　kernels　needed　to　cover　the　united　states　to　a　depth　of　ninemiles；　or　cupfuls　of　water　in　the　pacific　ocean；　or　soft　drink　cans　that　would；　evenly　stacked；　cover　the　earth　to　adepth　of　200　miles。　an　equivalent　number　of　american　pennies　would　be　enough　to　make　every　person　on　eartha　dollar　trillionaire。　it　is　a　big　number。

driven　in　large　part　by　developments　in　chemistry；　and　yet　as　an　organized　science　chemistrybarely　existed　for　decades。

the　chemical　society　of　london　was　not　founded　until　1841　and　didn’t　begin　to　produce　aregular　journal　until　1848；　by　which　time　most　learned　societies　in　britain—geological；geographical；　zoological；　horticultural；　and　linnaean　（for　naturalists　and　botanists）—were　atleast　twenty　years　old　and　often　much　more。　the　rival　institute　of　chemistry　didn’t　e　intobeing　until　1877；　a　year　after　the　founding　of　the　american　chemical　society。　becausechemistry　was　so　slow　to　get　organized；　news　of　avogadro’s　important　breakthrough　of　1811didn’t　begin　to　bee　general　until　the　first　international　chemistry　congress；　in　karlsruhe；in　1860。

because　chemists　for　so　long　worked　in　isolation；　conventions　were　slow　to　emerge。　untilwell　into　the　second　half　of　the　century；　the　formula　h2o2might　mean　water　to　one　chemistbut　hydrogen　peroxide　to　another。　c2h4could　signify　ethylene　or　marsh　gas。　there　was　hardlya　molecule　that　was　uniformly　represented　everywhere。

chemists　also　used　a　bewildering　variety　of　symbols　and　abbreviations；　often　self…invented。

sweden’s　j。　j。　berzelius　brought　a　much…needed　measure　of　order　to　matters　by　decreeing　thatthe　elements　be　abbreviated　on　the　basis　of　their　greek　or　latin　names；　which　is　why　theabbreviation　for　iron　is　fe　（from　the　latin　ferrum　）　and　that　for　silver　is　ag　（from　the　latinargentum　）。　that　so　many　of　the　other　abbreviations　accord　with　their　english　names　（n　fornitrogen；　o　for　oxygen；　h　for　hydrogen；　and　so　on）　reflects　english’s　latinate　nature；　not　itsexalted　status。　to　indicate　the　number　of　atoms　in　a　molecule；　berzelius　employed　asuperscript　notation；　as　in　h2o。　later；　for　no　special　reason；　the　fashion　became　to　render　thenumber　as　subscript：　h2o。

despite　the　occasional　tidyings…up；　chemistry　by　the　second　half　of　the　nineteenth　centurywas　in　something　of　a　mess；　which　is　why　everybody　was　so　pleased　by　the　rise　toprominence　in　1869　of　an　odd　and　crazed…looking　professor　at　the　university　of　st。　petersburgnamed　dmitri　ivanovich　mendeleyev。

mendeleyev　（also　sometimes　spelled　mendeleev　or　mendeléef）　was　born　in　1834　attobolsk；　in　the　far　west　of　siberia；　into　a　well…educated；　reasonably　prosperous；　and　verylarge　family—so　large；　in　fact；　that　history　has　lost　track　of　exactly　how　many　mendeleyevsthere　were：　some　sources　say　there　were　fourteen　children；　some　say　seventeen。　all　agree；　atany　rate；　that　dmitri　was　the　youngest。　luck　was　not　always　with　the　mendeleyevs。　whendmitri　was　small　his　father；　the　headmaster　of　a　local　school；　went　blind　and　his　mother　hadto　go　out　to　work。　clearly　an　extraordinary　woman；　she　eventually　became　the　manager　of　asuccessful　glass　factory。　all　went　well　until　1848；　when　the　factory　burned　down　and　thefamily　was　reduced　to　penury。　determined　to　get　her　youngest　child　an　education；　theindomitable　mrs。　mendeleyev　hitchhiked　with　young　dmitri　four　thousand　miles　to　st。

petersburg—that’s　equivalent　to　traveling　from　london　to　equatorial　guinea—and　depositedhim　at　the　institute　of　pedagogy。　worn　out　by　her　efforts；　she　died　soon　after。

mendeleyev　dutifully　pleted　his　studies　and　eventually　landed　a　position　at　the　localuniversity。　there　he　was　a　petent　but　not　terribly　outstanding　chemist；　known　more　forhis　wild　hair　and　beard；　which　he　had　trimmed　just　once　a　year；　than　for　his　gifts　in　thelaboratory。

however；　in　1869；　at　the　age　of　thirty…five；　he　began　to　toy　with　a　way　to　arrange　theelements。　at　the　time；　elements　were　normally　grouped　in　two　ways—either　by　atomic　weight（using　avogadro’s　principle）　or　by　mon　properties　（whether　they　were　metals　or　gases；for　instance）。　mendeleyev’s　breakthrough　was　to　see　that　the　two　could　be　bined　in　asingle　table。

as　is　often　the　way　in　science；　the　principle　had　actually　been　anticipated　three　yearspreviously　by　an　amateur　chemist　in　england　named　john　newlands。　he　suggested　that　whenelements　were　arranged　by　weight　they　appeared　to　repeat　certain　properties—in　a　sense　toharmonize—at　every　eighth　place　along　the　scale。　slightly　unwisely；　for　this　was　an　ideawhose　time　had　not　quite　yet　e；　newlands　called　it　the　law　of　octaves　and　likened　thearrangement　to　the　octaves　on　a　piano　keyboard。　perhaps　there　was　something　in　newlands’smanner　of　presentation；　but　the　idea　was　considered　fundamentally　preposterous　and　widelymocked。　at　gatherings；　droller　members　of　the　audience　would　sometimes　ask　him　if　he　couldget　his　elements　to　play　them　a　little　tune。　discouraged；　newlands　gave　up　pushing　the　ideaand　soon　dropped　from　view　altogether。

mendeleyev　used　a　slightly　different　approach；　placing　his　elements　into　groups　of　seven；but　employed　fundamentally　the　same　principle。　suddenly　the　idea　seemed　brilliant　andwondrously　perceptive。　because　the　properties　repeated　themselves　periodically；　the　inventionbecame　known　as　the　periodic　table。

mendeleyev　was　said　to　have　been　inspired　by　the　card　game　known　as　solitaire　in　northamerica　and　patience　elsewhere；　wherein　cards　are　arranged　by　suit　horizontally　and　bynumber　vertically。　using　a　broadly　similar　concept；　he　arranged　the　elements　in　horizontalrows　called　periods　and　vertical　columns　called　groups。　this　instantly　showed　one　set　ofrelationships　when　read　up　and　down　and　another　when　read　from　side　to　side。　specifically；the　vertical　columns　put　together　chemicals　that　have　similar　properties。　thus　copper　sits　ontop　of　silver　and　silver　sits　on　top　of　gold　because　of　their　chemical　affinities　as　metals；　whilehelium；　neon；　and　argon　are　in　a　column　made　up　of　gases。　（the　actual；　formal　determinant　inthe　ordering　is　something　called　their　electron　valences；　for　which　you　will　have　to　enroll　innight　classes　if　you　wish　an　understanding。）　the　horizontal　rows；　meanwhile；　arrange　thechemicals　in　ascending　order　by　the　number　of　protons　in　their　nuclei—what　is　known　as　theiratomic　number。

the　structure　of　atoms　and　the　significance　of　protons　will　e　in　a　following　chapter；　sofor　the　moment　all　that　is　necessary　is　to　appreciate　the　organizing　principle：　hydrogen　hasjust　one　proton；　and　so　it　has　an　atomic　number　of　one　and　es　first　on　the　chart；　uraniumhas　ninety…two　protons；　and　so　it　es　near　the　end　and　has　an　atomic　number　of　ninety…two。

in　this　sense；　as　philip　ball　has　pointed　out；　chemistry　really　is　just　a　matter　of　counting。

（atomic　number；　incidentally；　is　not　to　be　confused　with　atomic　weight；　which　is　the　numberof　protons　plus　the　number　of　neutrons　in　a　given　element。）　there　was　still　a　great　deal　thatwasn’t　known　or　un