Covalent vs Polar Covalent
Raws li tau hais los ntawm American chemist G. N. Lewis, atoms ruaj khov thaum lawv muaj yim electrons hauv lawv lub plhaub valence. Feem ntau ntawm cov atoms muaj tsawg tshaj li yim electrons nyob rau hauv lawv valence shells (tshwj tsis yog cov noble gases nyob rau hauv pab pawg neeg 18 ntawm lub periodic rooj); yog li ntawd, lawv tsis ruaj khov. Cov atoms no zoo li ua rau ib leeg, ua kom ruaj khov. Yog li, txhua lub atom tuaj yeem ua tiav cov roj hluav taws xob hluav taws xob zoo. Covalent bonds yog ib hom tshuaj lom neeg loj, uas txuas atoms hauv cov tshuaj lom neeg. Muaj ob hom ntawm covalent bonds uas tsis yog polar thiab polar covalent bonds.
Polarity tshwm sim vim qhov sib txawv ntawm electronegativity. Electronegativity muab ib qho kev ntsuas ntawm ib lub atom kom nyiam electrons nyob rau hauv ib daim ntawv cog lus. Feem ntau Pauling nplai yog siv los qhia txog qhov tseem ceeb ntawm electronegativity. Nyob rau hauv lub sij hawm lub sij hawm, muaj ib tug qauv raws li yuav ua li cas lub electronegativity qhov tseem ceeb hloov. Los ntawm sab laug mus rau sab xis los ntawm ib lub sij hawm, tus nqi electronegativity nce. Yog li ntawd, halogens muaj qhov tseem ceeb ntawm electronegativity loj dua nyob rau hauv ib lub sij hawm, thiab pawg 1 cov ntsiab lus muaj qhov sib piv qis electronegativity qhov tseem ceeb. Hauv cov pab pawg, cov txiaj ntsig electronegativity txo. Thaum ob ntawm tib lub atom los yog atoms muaj tib lub electronegativity tsim ib daim ntawv cog lus ntawm lawv, cov atoms rub lub electron khub nyob rau hauv ib txoj kev zoo sib xws. Yog li ntawd, lawv nyiam sib faib cov electrons thiab cov nyiaj no yog hu ua nonpolar covalent bonds.
Covalent Bond
Thaum ob lub atoms zoo sib xws lossis qis heev electronegativity sib txawv, hnov qab ua ke, lawv tsim ib daim ntawv cog lus los ntawm kev sib koom electrons. Ob lub atoms tuaj yeem tau txais cov roj hluav taws xob hluav taws xob zoo los ntawm kev sib koom electrons hauv txoj kev no. Molecule yog cov khoom uas tshwm sim los ntawm kev tsim ntawm covalent bonds ntawm atoms. Piv txwv li, thaum tib lub atoms koom ua ke los tsim cov molecules zoo li Cl2, H2, los yog P4, txhua lub atom raug khi rau lwm tus los ntawm covalent daim ntawv cog lus.
Polar Covalent
Nyob ntawm qhov sib txawv ntawm electronegativity, tus cwj pwm covalent tuaj yeem hloov pauv. Qhov kev sib txawv no yuav siab dua lossis qis dua. Yog li ntawd, daim ntawv cog lus electron khub yog rub ntau dua los ntawm ib lub atom piv rau lwm lub atom, uas yog koom nrog hauv kev ua daim ntawv cog lus. Qhov no yuav ua rau muaj kev faib tsis sib npaug ntawm electrons ntawm ob lub atoms. Thiab cov hom ntawm covalent bonds yog hu ua polar covalent bonds. Vim tias qhov sib faib tsis sib luag ntawm cov hluav taws xob, ib lub atom yuav muaj qhov tsis zoo me ntsis thaum lwm lub atom yuav muaj qhov zoo me ntsis. Hauv qhov piv txwv no, peb hais tias cov atoms tau txais ib feem tsis zoo lossis qhov zoo. Lub atom nrog lub siab dua electronegativity tau txais qhov tsis zoo me ntsis, thiab lub atom nrog qis electronegativity yuav tau txais qhov zoo me ntsis. Polarity txhais tau tias kev sib cais ntawm cov nqi. Cov molecules no muaj lub sijhawm dipole. Dipole lub sijhawm ntsuas qhov polarity ntawm daim ntawv cog lus, thiab nws feem ntau ntsuas hauv debyes (nws kuj muaj kev taw qhia).
Qhov txawv ntawm Covalent thiab Polar Covalent yog dab tsi?
• Polar covalent bonds yog ib hom ntawm covalent bonds.
• Covalent bonds, uas tsis yog-polar, yog tsim los ntawm ob lub atoms uas zoo sib xws electronegativities. Polar covalent bonds yog tsim los ntawm ob lub atom nrog electronegativities sib txawv (tab sis qhov sib txawv yuav tsum tsis txhob siab tshaj 1.7).
• Hauv cov ntawv cog lus uas tsis yog polar covalent, cov hluav taws xob sib npaug sib npaug los ntawm ob lub atoms koom ua cov ntawv cog lus. Nyob rau hauv polar covalent, cov electron khub yog rub ntau dua los ntawm ib lub atom piv rau lwm lub atom. Yog li qhov sib koom electron tsis sib npaug.
• Polar covalent daim ntawv cog lus muaj lub sijhawm dipole, qhov uas tsis yog polar covalent daim ntawv cog lus tsis muaj.
