Key Difference – VBT vs CFT
Lo lus VBT sawv cev rau txoj kev xav ntawm valence bond. Nws yog ib txoj kev xav siv los piav txog kev tsim cov tshuaj sib txawv ntawm cov atoms. Qhov kev xav no piav qhia txog kev sib tshooj lossis sib xyaw ntawm atomic orbitals los tsim cov tshuaj lom neeg. Lub sij hawm CFT stands rau Crystal field theory. Nws yog ib qho qauv tsim los piav qhia txog kev tawg ntawm degeneracies (electron plhaub ntawm lub zog sib npaug) ntawm electron orbitals (feem ntau yog d lossis f orbitals) vim qhov hluav taws xob zoo li qub uas tsim los ntawm ib puag ncig anion lossis anions (lossis ligands). Qhov sib txawv tseem ceeb ntawm VBT thiab CFT yog VBT piav qhia txog kev sib xyaw ntawm orbitals whereas CFT piav qhia kev sib cais ntawm orbitals.
VBT yog dab tsi
Lo lus VBT sawv cev rau txoj kev xav ntawm valence bond. Nws piav qhia txog cov tshuaj sib txuas ntawm covalent compound. Li no VBT piav qhia txog yuav ua li cas daim ntawv cog lus covalent raug tsim. Covalent daim ntawv cog lus yog tsim los ntawm kev sib koom ntawm electrons ntawm atoms. Atoms sib koom electrons los sau lawv cov teeb tsa hluav taws xob (lwm yam lawv tsis ruaj khov). Cov electrons sib koom los ntawm kev sib xyaw lossis sib tshooj ntawm atomic orbitals. Tab sis ua ntej kev sib tshooj tshwm sim, ntau qhov yuav tsum tau ua tiav.
Muaj ob hom kev sib cog lus sib cog lus ua sigma daim ntawv cog lus thiab pi daim ntawv cog lus. Cov nyiaj no yog tsim los ntawm kev sib tshooj ntawm atomic orbitals. Overlapping ntawm s orbitals ib txwm ua sigma daim ntawv cog lus. Overlapping ntawm p orbitals ua rau tsim cov pi bonds. Qhov sib tshooj ntawm s thiab p atomic orbitals ua rau kev tsim cov hybrid orbitals; li no, tus txheej txheem hu ua hybridization.
Daim duab 01: Kev sib xyaw ntawm 2s thiab 2p Orbitals
Muaj peb qhov loj hybrid orbitals uas tuaj yeem tsim tau:
- sp Hybrid Orbital - Tsim los ntawm hybridization ntawm ib qho s thiab ib qho p orbital.
- sp2 Hybrid Orbital - Tsim los ntawm hybridization ntawm ib qho thiab ob lub p orbitals.
- sp3 Hybrid Orbital - Tsim los ntawm hybridization ntawm ib qho s thiab peb p orbitals.
CFT yog dab tsi?
Lub sij hawm CFT stands rau Crystal field theory. Crystals teb txoj kev xav yog ib qho qauv tsim los piav qhia txog kev tawg ntawm degeneracies (electron plhaub ntawm lub zog sib npaug) ntawm electron orbitals (feem ntau yog d lossis f orbitals) vim qhov hluav taws xob zoo li qub uas tsim los ntawm ib puag ncig anion lossis anions (lossis ligands). Crystal field theory feem ntau yog siv los ua kom pom tus cwj pwm ntawm kev hloov hlau ions complexes. Qhov kev xav no tseem tuaj yeem piav qhia txog cov khoom sib nqus, xim ntawm kev sib koom ua ke, hydration enthalpies, thiab lwm yam.
Theory
Kev sib cuam tshuam ntawm cov hlau ion thiab ligands yog vim qhov kev nyiam ntawm cov hlau ion nrog cov nqi zoo thiab cov tsis muaj hluav taws xob tsis sib xws (tus nqi tsis zoo) ntawm ligand. Qhov kev xav no feem ntau yog los ntawm kev hloov pauv uas tshwm sim hauv tsib degenerate d electron orbitals (ib lub atom hlau muaj tsib d orbitals). Thaum ib lub ligand los ze rau ntawm cov hlau ion, cov electrons uas tsis tau ua ke yog ze rau qee qhov d orbitals thaum piv nrog lwm cov d orbitals ntawm cov hlau ion. Qhov no ua rau poob ntawm degeneracy. Cov electrons nyob rau hauv lub d orbitals repel cov electrons ntawm lub ligand (ob leeg yog tsis zoo them). Yog li cov d orbitals uas nyob ze rau lub ligand muaj lub zog siab dua lwm cov d orbitals. Qhov no ua rau kev sib cais ntawm d orbitals rau hauv siab zog d orbitals thiab qis zog d orbitals, raws li lub zog.
Qee yam cuam tshuam rau qhov kev sib cais no suav nrog xwm txheej ntawm cov hlau ion, oxidation lub xeev ntawm cov hlau ion, kev npaj ntawm ligands nyob ib ncig ntawm lub hauv paus hlau ion thiab qhov xwm ntawm ligands. Tom qab kev sib cais ntawm cov d orbitals raws li lub zog, qhov sib txawv ntawm qhov siab thiab qis zog d orbitals yog hu ua crystal-filed splitting parameter (∆ octrau octahedral complexes).
Daim duab 02: Sib faib qauv hauv Octahedral Complexes
Splitting Pattern
Vim tias muaj tsib d orbitals, qhov sib cais tshwm sim hauv qhov piv ntawm 2: 3. Nyob rau hauv octahedral complexes, ob lub orbitals yog nyob rau hauv lub siab zog theem (piv txwv li) thiab peb orbitals nyob rau hauv qis zog theem (collectively hu ua t2g). Nyob rau hauv tetrahedral complexes, qhov opposite tshwm sim; peb lub orbitals yog nyob rau hauv qib siab zog thiab ob nyob rau hauv qis zog theem.
Qhov txawv ntawm VBT thiab CFT yog dab tsi?
VBT vs CFT |
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| Lub sij hawm VBT stands for valence bond theory. | Lub sij hawm CFT stands rau Crystal field theory. |
| Theory | |
| VBT yog ib txoj kev xav uas piav qhia txog kev tsim cov nyiaj cog lus los ntawm kev sib xyaw ntawm atomic orbitals. | CFT yog tus qauv tsim los piav qhia txog kev tawg ntawm degeneracies ntawm electron orbitals vim hluav taws xob zoo li qub uas tsim los ntawm ib puag ncig anion lossis anions |
| piav qhia | |
| VBT piav qhia txog kev sib xyaw ntawm orbitals. | CFT piav qhia qhov sib cais ntawm orbitals. |
Summary – VBT vs CFT
Lo lus VBT sawv cev rau txoj kev xav ntawm valence bond. Lub sij hawm CFT stands rau crystal field theory. Qhov sib txawv tseem ceeb ntawm VBT thiab CFT yog VBT piav qhia kev sib xyaw ntawm orbitals whereas CFT piav qhia kev sib cais ntawm orbitals.
