Imibuzo Yezibonelo Ekhuluma Ngezimo Zama-Molecular
I-Pengantar
I-Chemistry iwukufunda ngokuziphatha kwezinto kanye nezinguquko ezidlula kuzo. Umqondo owodwa obalulekile ku-chemistry ukuqonda ukuma kwama-molecule. Ukuma kwama-molecule kuthonya izakhiwo zomzimba nezamakhemikhali zama-compound, njengephuzu lokuncibilika, iphuzu lokubila, kanye nomfutho womusi. Ukuma kwama-molecule nakho kudlala indima ebalulekile ekunqumeni ukusabela kwamakhemikhali okwenzeka kulawo ma-compound. Ithiyori esetshenziswa kakhulu ukuchaza ukuma kwama-molecule ithiyori ye-VSEPR (Valence Shell Electron Pair Repulsion). Kulesi sihloko, sizoxoxa ngezibonelo eziningana zezinkinga ezihilela ukuma kwama-molecule kanye nendlela ithiyori ye-VSEPR engasetshenziswa ngayo ukuzixazulula.
Ithiyori ye-VSEPR
Ithiyori ye-VSEPR iyithiyori esetshenziselwa ukunquma ukuma kwama-molecule ngokusekelwe ekuxoshweni kwama-electron pair azungeze i-athomu ephakathi. Ngokwalo mbono, ama-electron pair azohlela ngendlela yokuthi ukuxoshwa phakathi kwawo kuncishiswe. Lokhu kubangela ukuthi i-molecule ithathe isimo esithile, esibikezelwayo. La ma-electron pair afaka phakathi ama-electron pair ahlanganisa ama-bonding pairs (BEPs) kanye nama-electron pairs azimele (LOPs).
Ezinye zezinhlobo zama-molecule ezikhiqizwayo ngokuvamile ziyi:
1. Umugqa oqondile
2. Ipulani Eyinxantathu
3. I-Tetrahedral
4. I-Trigonal Bipyramidal
5. I-Octahedral
6. Ukugoba (ukugoba)
7. I-seesaw
8. Okumise okwe-T
9. Ipulani Yesikwele
10. Isikwele Esiyi-Pyramidal
Okulandelayo, ake sibheke eminye imibuzo eyisibonelo kanye nezingxoxo zayo.
Isibonelo Umbuzo 1: Ukunquma Isimo Sama-molecule e-CH4
Umbuzo:
Thola ukuma kwe-molecular ye-methane (CH4) usebenzisa i-VSEPR theory.
Ingxoxo:
1. Thola isakhiwo sikaLewis:
– I-athomu ephakathi: C (ikhabhoni)
– Ikhabhoni inama-electron angu-4 e-valence.
– I-hydrogen ngayinye ine-valence electron eyodwa.
– Ama-electron e-valence aphelele = 4 (C) + 4 x 1 (H) = ama-electron e-valence ayi-8.
Isakhiwo sikaLewis se-CH4 sibonisa ikhabhoni phakathi nendawo enama-athomu amane e-hydrogen akha izibopho ezilodwa (sigma) ku-athomu yekhabhoni. Azikho izibhangqwana ezilodwa zama-electron ku-athomu yekhabhoni.
2. Ukubala Ama-Electron Pairs:
– I-PEI: Kunezibopho ezine, zonke eziyizibhangqa zama-electron ezibophayo.
– I-PEB: Azikho izibhangqwana zama-electron ezizimele.
3. Ukuhlonza Izimo Zama-Molecular:
– Njengoba i-PEI engu-4 kanye ne-PEB engu-0 iyonke, ukusatshalaliswa kwama-electron azungeze i-athomu ephakathi kuzothatha isimo esinciphisa ukuxoshwa.
– Uhlobo olusabalaliswa kude kakhulu yi-Tetrahedral.
Ngakho-ke, ukuma kwe-molecule ye-CH4 kuyi-tetrahedral ene-engeli yesibopho esingama-degrees angu-109.5.
Isibonelo Umbuzo 2: Ukunquma Isimo Se-Molecular se-NH3
Umbuzo:
Thola ukuma kwe-ammonia (NH3) usebenzisa i-VSEPR theory.
Ingxoxo:
1. Thola isakhiwo sikaLewis:
– I-athomu ephakathi: N (i-nitrogen).
– I-nitrogen inama-electron angu-5 e-valence.
– I-hydrogen ngayinye ine-valence electron eyodwa.
– Ama-electron e-valence aphelele = 5 (N) + 3 x 1 (H) = ama-electron e-valence ayi-8.
Isakhiwo sikaLewis se-NH3 sibonisa i-nitrogen phakathi nendawo enama-athomu amathathu e-hydrogen akha izibopho ezilodwa (sigma) ne-athomu ye-nitrogen kanye nepheya elilodwa lama-electron ku-nitrogen.
2. Ukubala Ama-Electron Pairs:
– I-PEI: Kunezibopho ezintathu, zonke eziyizibhangqa zama-electron ezibophayo.
– I-PEB: Kukhona i-electron pair eyodwa eyodwa.
3. Ukuhlonza Izimo Zama-Molecular:
– Njengoba i-PEI engu-3 kanye ne-PEB engu-1 iyonke, ukusatshalaliswa kwama-electron azungeze i-athomu ephakathi kuzothatha isimo esinciphisa ukuxoshwa.
– Isimo esinokwabiwa okufanele yi-Trigonal Pyramidal.
Ngakho-ke, ukuma kwe-molecule ye-NH3 kuyi-pyramidal enxantathu ene-engeli yesibopho engaphansi kancane kwama-degrees angu-109.5 ngenxa yokuxoshwa yi-single electron pair enamandla.
Isibonelo Umbuzo 3: Ukunquma Isimo Sama-molecule e-H2O
Umbuzo:
Thola ukuma kwe-molecule yamanzi (H2O) usebenzisa i-VSEPR theory.
Ingxoxo:
1. Thola isakhiwo sikaLewis:
– I-athomu ephakathi: O (umoya-mpilo).
– I-oksijini inama-electron angu-6 e-valence.
– I-hydrogen ngayinye ine-valence electron eyodwa.
– Ama-electron e-valence aphelele = 6 (O) + 2 x 1 (H) = ama-electron e-valence ayi-8.
Isakhiwo sikaLewis se-H2O sibonisa umoya-mpilo phakathi nendawo enama-athomu amabili e-hydrogen akha izibopho ezilodwa (sigma) ne-athomu ye-oxygen kanye nama-electron amabili azimele emoyeni.
2. Ukubala Ama-Electron Pairs:
– I-PEI: Kunezibopho ezintathu, zonke eziyizibhangqa zama-electron ezibophayo.
– I-PEB: Kukhona i-electron pair eyodwa eyodwa.
3. Ukuhlonza Izimo Zama-Molecular:
– Njengoba i-PEI engu-2 kanye ne-PEB engu-2 iyonke, ukusatshalaliswa kwama-electron azungeze i-athomu ephakathi kuzothatha isimo esinciphisa ukuxoshwa.
– Isimo esinokwabiwa okufanele yi-Bent.
Ngakho-ke, ukuma kwe-molecule ye-H2O kugobile nge-engeli yesibopho esingama-degrees angu-104.5.
Isibonelo Umbuzo 4: Ukunqunywa Kwesimo Se-Molecular se-PCl5
Umbuzo:
Thola ukuma kwe-molecule ye-phosphorus pentachloride (PCl5) usebenzisa i-VSEPR theory.
Ingxoxo:
1. Thola isakhiwo sikaLewis:
– I-athomu ephakathi: P (i-phosphorus).
– I-Phosphorus inama-electron angu-5 e-valence.
– I-chlorine ngayinye inama-electron angu-7 e-valence.
– Ama-electron e-valence aphelele = 5 (P) + 5 x 7 (Cl) = ama-electron e-valence angu-40.
Isakhiwo sikaLewis se-PCl5 sibonisa i-phosphorus phakathi nendawo enama-athomu amahlanu e-chlorine akha izibopho ezilodwa (sigma) ne-athomu ye-phosphorus. Azikho izinhlangothi ezimbili zama-electron ku-phosphorus.
2. Ukubala Ama-Electron Pairs:
– I-PEI: Kunezibopho ezintathu, zonke eziyizibhangqa zama-electron ezibophayo.
– I-PEB: Azikho izibhangqwana zama-electron ezizimele.
3. Ukuhlonza Izimo Zama-Molecular:
– Njengoba i-PEI engu-5 kanye ne-PEB engu-0 iyonke, ukusatshalaliswa kwama-electron azungeze i-athomu ephakathi kuzothatha isimo esinciphisa ukuxoshwa.
– Isimo esinokwabiwa okufanele yi-Trigonal Bipyramidal.
Ngakho-ke, ukuma kwe-molecule ye-PCl5 kuyi-trigonal bipyramidal enama-engeli e-bond angu-90° no-120°.
Isibonelo Umbuzo 5: Ukunqunywa Kokuma Kwama-Molecule e-SF6
Umbuzo:
Thola ukuma kwe-molecular ye-sulfur hexafluoride (SF6) usebenzisa i-VSEPR theory.
Ingxoxo:
1. Thola isakhiwo sikaLewis:
– I-athomu ephakathi: S (isulfure).
– I-sulfur inama-electron angu-6 e-valence.
– I-fluorine ngayinye inama-electron angu-7 e-valence.
– Ama-electron e-valence aphelele = 6 (S) + 6 x 7 (F) = ama-electron e-valence angu-48.
Isakhiwo sikaLewis se-SF6 sibonisa isibabule phakathi nendawo nama-athomu ayisithupha e-fluorine akha izibopho ezilodwa (sigma) ne-athomu ye-sulfur. Azikho izibhangqa ezilodwa zama-electron esibabuleni.
2. Ukubala Ama-Electron Pairs:
– I-PEI: Kunezibopho ezintathu, zonke eziyizibhangqa zama-electron ezibophayo.
– I-PEB: Azikho izibhangqwana zama-electron ezizimele.
3. Ukuhlonza Izimo Zama-Molecular:
– Njengoba i-PEI engu-6 kanye ne-PEB engu-0 iyonke, ukusatshalaliswa kwama-electron azungeze i-athomu ephakathi kuzothatha isimo esinciphisa ukuxoshwa.
– Isimo esinokwabiwa okufanele yi-Octahedral.
Ngakho-ke, ukuma kwe-molecule ye-SF6 kuyi-octahedral ene-engeli yesibopho engu-90°.
Isiphetho
Ukuqonda ukuma kwama-molecule kubalulekile ekuchazeni izakhiwo eziningi zamakhemikhali nezomzimba ze-compound. Ithiyori ye-VSEPR inikeza indlela ephumelelayo yokubikezela i-geometry yayo ngokusekelwe ekubalweni kokubopha kanye nama-pair azimele. Esibonelweni ngasinye esixoxwe ngaso, inqubo ihilela ukunquma isakhiwo se-Lewis, ukubala ama-pair ama-electron, bese ekugcineni ukuthola isimo sama-molecule esifanele kakhulu. Ngokuzijwayeza njalo, noma ubani angaba nekhono lokusebenzisa ithiyori ye-VSEPR ukuthola isimo sama-molecule.
