Vim li cas atoms tuaj yeem sib xyaw ua ke los tsim cov molecules? Dab tsi yog vim li cas rau qhov muaj peev xwm ntawm cov khoom, uas suav nrog atoms ntawm cov tshuaj sib txawv kiag li? Cov no yog cov teeb meem thoob ntiaj teb cuam tshuam rau cov ntsiab lus tseem ceeb ntawm kev tshawb fawb lub cev thiab tshuaj lom neeg niaj hnub. Koj tuaj yeem teb lawv, muaj lub tswv yim hais txog cov qauv hluav taws xob ntawm atoms thiab paub txog cov yam ntxwv ntawm covalent daim ntawv cog lus, uas yog lub hauv paus rau feem ntau cov chav kawm sib txuas. Lub hom phiaj ntawm peb tsab xov xwm yog kom paub txog cov txheej txheem ntawm kev tsim ntawm ntau hom tshuaj bonds thiab cov yam ntxwv ntawm cov khoom ntawm cov tebchaw uas muaj nyob rau hauv lawv cov molecules.
Cov qauv hluav taws xob ntawm lub atom
Electroneutral particles ntawm teeb meem, uas yog nws cov yam ntxwv, muaj ib tug qauv uas tsom rau cov qauv ntawm lub hnub ci system. Raws li cov ntiaj chaw revolve nyob ib ncig ntawm lub hnub qub nruab nrab - lub hnub, yog li cov electrons nyob rau hauv lub atom tsiv mus nyob ib ncig ntawm lub zoo nqi nucleus. Ua tus cwj pwmNyob rau hauv covalent daim ntawv cog lus, cov electrons nyob rau hauv lub xeem lub zog thiab qhov deb tshaj plaws ntawm lub nucleus yuav yog ib qho tseem ceeb. Txij li thaum lawv qhov kev sib txuas nrog qhov chaw ntawm lawv tus kheej atom yog tsawg, lawv tuaj yeem yooj yim nyiam los ntawm cov nuclei ntawm lwm cov atoms. Qhov no yog qhov tseem ceeb heev rau qhov tshwm sim ntawm kev sib cuam tshuam ntawm kev sib cuam tshuam ua rau kev tsim cov molecules. Vim li cas cov molecular daim ntawv yog hom tseem ceeb ntawm kev muaj teeb meem ntawm peb lub ntiaj teb? Cia peb kawm.
Basic khoom ntawm atoms
Lub peev xwm ntawm cov khoom siv hluav taws xob nruab nrab hauv kev sib cuam tshuam, ua rau muaj kev nce hauv lub zog, yog lawv qhov tseem ceeb tshaj plaws. Tseeb tiag, nyob rau hauv ib txwm muaj xwm txheej, lub xeev molecular ntawm cov teeb meem yog ruaj khov dua li lub xeev atomic. Cov kev cai tseem ceeb ntawm niaj hnub atomic thiab molecular txoj kev xav piav qhia ob qho tib si hauv paus ntsiab lus ntawm kev tsim cov molecules thiab cov yam ntxwv ntawm covalent daim ntawv cog lus. Nco qab tias lub zog sab nraud ntawm lub atom tuaj yeem muaj los ntawm 1 txog 8 electrons, nyob rau hauv rooj plaub tom kawg, txheej yuav ua tiav, uas txhais tau tias nws yuav ruaj khov heev. Atoms ntawm noble gases muaj xws li ib tug txheej txheem theem: argon, krypton, xenon - inert ntsiab uas ua kom tiav txhua lub sij hawm nyob rau hauv lub system ntawm D. I. Mendeleev. Qhov kev zam ntawm no yog helium, uas tsis muaj 8, tab sis tsuas yog 2 electrons nyob rau theem kawg. Yog vim li cas yooj yim: nyob rau hauv thawj lub sij hawm muaj tsuas yog ob lub ntsiab uas nws atoms muaj ib tug electron txheej. Tag nrho lwm yam tshuaj muaj los ntawm 1 mus rau 7 electrons nyob rau hauv kawg, tsis tiav txheej. Nyob rau hauv tus txheej txheem ntawm interacting nrog ib leeg, lub atoms yuavsiv zog ua kom muaj cov khoom siv hluav taws xob mus txog rau ib qho octet thiab rov kho qhov kev teeb tsa ntawm ib qho atom ntawm cov khoom tsis muaj zog. Xws li lub xeev tuaj yeem ua tiav ob txoj hauv kev: los ntawm kev poob ntawm ib tus kheej lossis los ntawm kev lees txais cov khoom tsis zoo txawv teb chaws. Cov qauv kev sib cuam tshuam no piav qhia seb yuav txiav txim siab seb puas muaj ionic lossis covalent daim ntawv cog lus yuav tsim ntawm cov atoms reacting.
Mechanisms rau kev tsim cov khoom siv hluav taws xob ruaj khov
Cia peb xav txog tias ob yam yooj yim nkag mus rau hauv cov tshuaj tiv thaiv ntawm cov tshuaj: hlau sodium thiab gaseous chlorine. Ib yam khoom ntawm chav kawm ntsev yog tsim - sodium chloride. Nws muaj ib hom ionic ntawm chemical bond. Vim li cas thiab nws tuaj txog li cas? Cia peb tig rov qab mus rau cov qauv ntawm cov atom ntawm cov khoom pib. Sodium tsuas muaj ib tug electron nyob rau hauv lub xeem txheej, tsis muaj zog khi rau lub nucleus vim lub vojvoog loj ntawm lub atom. Lub zog ionization ntawm tag nrho cov alkali hlau, uas suav nrog sodium, yog tsawg. Yog li ntawd, lub electron ntawm txheej txheej tawm ntawm lub zog theem, yog attracted los ntawm lub nucleus ntawm chlorine atom thiab tseem nyob rau hauv nws qhov chaw. Qhov no tsim ib qho piv txwv rau kev hloov pauv ntawm Cl atom mus rau hauv daim ntawv ntawm qhov tsis zoo ion. Tam sim no peb tsis cuam tshuam nrog cov khoom siv hluav taws xob tsis zoo, tab sis nrog cov nqi sodium cations thiab chlorine anions. Raws li kev cai lij choj ntawm physics, electrostatic attraction rog tshwm sim ntawm lawv, thiab cov compound tsim ib ionic siv lead ua lattice. Cov txheej txheem ntawm kev tsim cov ionic hom ntawm cov tshuaj cog lus txiav txim siab los ntawm peb yuav pab kom paub meej txog qhov tshwj xeeb thiab cov yam ntxwv tseem ceeb ntawm daim ntawv cog lus kom meej meej.
sib koom electron khub
Yog tias daim ntawv cog lus ionic tshwm sim ntawm cov atoms ntawm cov ntsiab lus uas txawv heev hauv electronegativity, piv txwv li, hlau thiab tsis yog hlau, ces hom covalent tshwm sim thaum atoms ntawm tib yam lossis txawv cov ntsiab lus tsis yog xim hlau sib cuam tshuam. Nyob rau hauv thawj rooj plaub, nws yog kev cai los tham txog cov uas tsis yog-polar, thiab nyob rau hauv lwm yam, hais txog lub polar daim ntawv ntawm ib tug covalent daim ntawv cog lus. Cov txheej txheem ntawm lawv cov kev tsim muaj ntau: txhua lub atoms ib nrab muab cov electrons rau kev siv, uas yog ua ke ua khub. Tab sis qhov spatial kev npaj ntawm electron khub txheeb ze rau nuclei ntawm atoms yuav txawv. Rau lub hauv paus no, hom covalent bonds yog txawv - tsis-polar thiab polar. Feem ntau, hauv cov tshuaj sib xyaw ua ke uas muaj cov atom ntawm cov khoom tsis yog xim hlau, muaj cov khub uas muaj cov khoom siv hluav taws xob nrog cov lus sib txawv, piv txwv li, tig ib ncig ntawm lawv cov nuclei hauv cov lus qhia. Txij li thaum lub zog ntawm cov khoom tsis zoo nyob rau hauv qhov chaw ua rau tsim cov huab cua electron, uas thaum kawg xaus rau hauv lawv qhov sib tshooj. Dab tsi yog qhov tshwm sim ntawm cov txheej txheem no rau atoms thiab nws ua rau dab tsi?
Lub cev muaj zog ntawm daim ntawv cog lus covalent
Nws hloov tawm tias ntawm nruab nrab ntawm ob qhov sib cuam tshuam atoms muaj ob-electron huab nrog lub siab ceev. Lub zog electrostatic ntawm kev nyiam ntawm huab cua tsis zoo nws tus kheej thiab cov nuclei ntawm atoms nce. Ib feem ntawm lub zog raug tso tawm thiab qhov kev ncua deb ntawm cov chaw atomic txo. Piv txwv li, thaum pib ntawm kev tsim cov molecule H2 qhov kev ncua deb ntawm nuclei ntawm hydrogen atomsyog 1.06 A, tom qab sib tshooj ntawm huab thiab tsim ntawm ib qho kev sib koom ua ke ntawm electron - 0.74 A. Piv txwv ntawm covalent daim ntawv cog lus tsim raws li cov txheej txheem saum toj no tuaj yeem pom ob qho tib si ntawm cov khoom siv yooj yim thiab tsis yooj yim. Nws lub ntsiab qhov txawv yog qhov muaj cov khoom siv hluav taws xob ntau. Raws li qhov tshwm sim, tom qab qhov tshwm sim ntawm kev sib cog lus ntawm cov atoms, piv txwv li, hydrogen, lawv txhua tus tau txais kev teeb tsa hluav taws xob ntawm inert helium, thiab cov txiaj ntsig molecule muaj cov qauv ruaj khov.
Spatial shape of a molecule
Lwm yam khoom tseem ceeb ntawm lub cev ntawm daim ntawv cog lus yog kev coj ua. Nws nyob ntawm qhov chaw configuration ntawm cov khoom molecule. Piv txwv li, thaum ob lub tshuab hluav taws xob sib tshooj nrog cov huab cua kheej kheej, qhov pom ntawm cov molecule yog linear (hydrogen chloride lossis hydrogen bromide). Cov duab ntawm cov dej molecules, nyob rau hauv uas s- thiab p- huab hybridize, yog angular, thiab muaj zog hais heev ntawm gaseous nitrogen zoo li lub pyramid.
qauv ntawm cov khoom yooj yim - non-metals
Tau paub tias hom ntawv cog lus twg yog hu ua covalent, nws muaj dab tsi, tam sim no nws yog lub sijhawm los daws nws ntau yam. Yog tias cov atoms ntawm tib yam tsis yog hlau - chlorine, nitrogen, oxygen, bromine, thiab lwm yam, cuam tshuam nrog ib leeg, ces cov khoom siv yooj yim raug tsim. Lawv cov khoom siv hluav taws xob zoo sib xws nyob ntawm tib qhov deb ntawm qhov chaw ntawm cov atoms, tsis muaj kev hloov pauv. Rau cov tebchaw uas tsis yog-polar hom ntawm covalent daim ntawv cog lus, cov yam ntxwv hauv qab no yog qhov tshwm sim: cov ntsiab lus qis boiling thiabmelting, insolubility hauv dej, dielectric zog. Tom ntej no, peb yuav pom tias cov tshuaj twg yog tus cwj pwm los ntawm covalent daim ntawv cog lus, nyob rau hauv qhov kev hloov ntawm cov khoom siv hluav taws xob tshwm sim.
Electronegativity thiab nws cov txiaj ntsig ntawm hom tshuaj lom neeg daim ntawv cog lus
Cov cuab yeej ntawm ib lub caij los nyiam cov khoom siv hluav taws xob los ntawm ib qho atom ntawm lwm cov khoom hauv chemistry hu ua electronegativity. Qhov ntsuas ntawm qhov muaj nuj nqis rau qhov ntsuas no, tau thov los ntawm L. Pauling, tuaj yeem pom hauv txhua phau ntawv qhia txog inorganic thiab general chemistry. Nws tus nqi siab tshaj plaws - 4.1 eV - muaj fluorine, qhov me dua - lwm yam tsis muaj hlau, thiab qhov ntsuas qis tshaj yog ib txwm muaj rau cov hlau alkali. Yog hais tias cov ntsiab lus sib txawv hauv lawv cov electronegativity react nrog ib leeg, ces inevitably ib, ntau active, yuav nyiam tsis zoo nqi hais txog ib tug atom ntawm ib tug passive lub caij rau nws cov nucleus. Yog li, lub cev lub cev ntawm covalent daim ntawv cog lus ncaj qha nyob ntawm lub peev xwm ntawm cov khoom los pub cov khoom siv hluav taws xob rau kev siv. Qhov tshwm sim ua khub tsis nyob rau hauv symmetrically nrog kev hwm rau lub nuclei, tab sis tau hloov mus rau lub zog ntau dua.
Txoj kev sib txuas nrog daim ntawv cog lus polar
Cov khoom nyob rau hauv molecules uas sib koom ua ke electron khub yog asymmetric nrog rau lub nuclei ntawm atoms muaj xws li hydrogen halides, acids, cov tebchaw ntawm chalcogens nrog hydrogen thiab acid oxides. Cov no yog sulfate thiab nitrate acids, oxides ntawm leej faj thiab phosphorus, hydrogen sulfide, thiab lwm yam. Piv txwv li, ib tug hydrogen chloride molecule muaj ib tug ntau electron khub,tsim los ntawm unpaired electrons ntawm hydrogen thiab chlorine. Nws tau txav los ze rau qhov chaw ntawm Cl atom, uas yog ib qho khoom siv hluav taws xob ntau dua. Tag nrho cov khoom uas muaj lub ncov qaumteb qabteb daim ntawv cog lus nyob rau hauv aqueous daws dissociate rau ions thiab ua ib tug hluav taws xob tam sim no. Cov khoom sib xyaws uas muaj cov ntawv cog lus polar covalent, cov piv txwv uas peb tau muab, kuj tseem muaj cov ntsiab lus melting ntau dua thiab kub kub piv rau cov khoom tsis yog hlau yooj yim.
Txoj kev rau kev rhuav tshem cov tshuaj lom neeg
Hauv cov tshuaj lom neeg, cov kev hloov pauv ntawm cov dej saturated hydrocarbons nrog halogens ua raws li cov txheej txheem radical. Ib qho kev sib xyaw ntawm methane thiab chlorine nyob rau hauv lub teeb thiab ntawm qhov kub thiab txias reacts nyob rau hauv xws li ib txoj kev uas cov tshuaj chlorine molecules pib sib cais mus rau hauv cov khoom uas nqa unpaired electrons. Hauv lwm lo lus, kev puas tsuaj ntawm cov khoom siv hluav taws xob zoo sib xws thiab kev tsim cov active radicals -Cl raug pom. Lawv muaj peev xwm cuam tshuam methane molecules nyob rau hauv xws li ib txoj kev uas lawv rhuav cov covalent daim ntawv cog lus ntawm carbon thiab hydrogen atoms. Ib qho active particle -H yog tsim, thiab cov dawb valency ntawm cov pa roj carbon atom yuav siv sij hawm ib tug chlorine radical, thiab chloromethane ua thawj cov khoom ntawm cov tshuaj tiv thaiv. Xws li ib tug mechanism rau splitting ntawm molecules yog hu ua homolytic. Yog hais tias tus khub ntawm electrons tag nrho dhau mus rau hauv ib qho ntawm cov atoms, ces lawv hais txog ib tug heterolytic mechanism yam ntxwv ntawm cov tshuaj tiv thaiv nyob rau hauv aqueous daws. Nyob rau hauv cov ntaub ntawv no, polar dej molecules yuav nce tus nqi ntawm kev puas tsuaj ntawm cov tshuaj bonds ntawm yaj compound.
ob npaug thiab triplelinks
Feem ntau ntawm cov organic thiab qee cov tshuaj inorganic muaj nyob hauv lawv cov molecules tsis yog ib qho, tab sis ob peb hom electron khub. Lub multiplicity ntawm covalent daim ntawv cog lus txo qhov kev ncua deb ntawm atoms thiab ua rau kom cov stability ntawm cov tebchaw. Lawv feem ntau hu ua chemically resistant. Piv txwv li, nyob rau hauv ib tug nitrogen molecule muaj peb khub ntawm electrons, lawv tau qhia nyob rau hauv cov qauv qauv los ntawm peb dashes thiab txiav txim nws lub zog. Cov khoom siv yooj yim nitrogen yog cov tshuaj tsis muaj zog thiab tuaj yeem cuam tshuam nrog lwm cov tebchaw, xws li hydrogen, oxygen lossis hlau, tsuas yog thaum cua sov lossis siab siab, nrog rau muaj cov catalysts.
Ob npaug thiab triple daim ntawv cog lus muaj nyob rau hauv xws li cov chav kawm ntawm cov organic tebchaw li unsaturated diene hydrocarbons, nrog rau cov khoom ntawm ethylene los yog acetylene series. Ntau daim ntawv cog lus txiav txim siab cov khoom siv tshuaj lom neeg tseem ceeb: ntxiv thiab cov tshuaj tiv thaiv polymerization tshwm sim ntawm cov ntsiab lus ntawm lawv qhov so.
Hauv peb tsab xov xwm, peb tau muab cov lus piav qhia dav dav ntawm daim ntawv cog lus thiab tshuaj xyuas nws hom tseem ceeb.
