Cov Lus Nug Piv Txwv Sib Tham Txog Covalent Bonds
Pendahuluuan
Ib daim ntawv cog lus covalent yog ib hom kev sib txuas tshuaj uas ob lub atoms sib koom ib khub lossis ntau dua electrons kom ua tiav qhov kev teeb tsa electron ruaj khov, xws li hauv cov pa roj tsw qab. Daim ntawv cog lus no feem ntau tshwm sim ntawm cov atoms tsis yog hlau uas muaj cov electronegativities siab thiab tsis sib txawv ntau. Kev tsim cov ntawv cog lus Covalent ua lub luag haujlwm tseem ceeb hauv ob qho tib si organic thiab inorganic chemistry thiab yog lub hauv paus ntawm ntau cov tshuaj uas peb ntsib txhua hnub. Hauv tsab xov xwm no, peb yuav tham txog ntau qhov piv txwv uas cuam tshuam nrog cov ntawv cog lus covalent thiab muab cov kev daws teeb meem los pab peb nkag siab zoo dua lawv.
Cov Lus Nug Piv Txwv thiab Kev Sib Tham
Lo lus nug thib 1
Txheeb xyuas hom thiab tus naj npawb ntawm cov bonds covalent uas tsim nyob rau hauv H2O (dej) molecule.
Kev Sib Tham:
Ib lub molecule dej muaj ib lub atom oxygen (O) thiab ob lub atom hydrogen (H).
1. Kev Teeb tsa Hluav Taws Xob:
– Cov pa oxygen: 1s² 2s² 2p⁴ (tag nrho 8 lub electrons)
– Hydrogen: 1s¹ (tag nrho 1 electron)
Cov pa oxygen xav tau ob lub electrons ntxiv kom ua tiav ib qho octet configuration (8 electrons hauv nws lub plhaub sab nraud tshaj plaws), thaum txhua lub hydrogen atom xav tau ib lub electron kom ua tiav ib qho duplet configuration (2 electrons hauv K plhaub).
2. Kev Tsim Cov Kev Sib Koom Tes:
- Txhua lub hydrogen atom sib koom ib lub electron nrog ib lub oxygen atom.
- Oxygen sib koom ob lub electrons nrog ob lub Hydrogen atoms, ib qho rau txhua lub atom.
Yog li, ob lub covalent bonds raug tsim nyob rau hauv H2O molecule, ib qho ntawm Oxygen atom thiab Hydrogen atom feem.
Lo lus nug thib 2
Sau cov qauv Lewis rau lub molecule methane (CH₄).
Kev Sib Tham:
Methane muaj ib lub carbon atom (C) thiab plaub lub hydrogen atoms (H).
1. Kev Teeb tsa Hluav Taws Xob:
- Cov pa roj carbon: 1s² 2s² 2p² (tag nrho 6 lub electrons)
– Hydrogen: 1s¹ (tag nrho 1 electron)
Cov pa roj carbon muaj plaub lub electrons valence (2s² 2p²), thiab xav tau plaub lub electrons ntxiv kom ncav cuag ib qho octet.
2. Kev Tsim Cov Kev Sib Koom Tes:
- Txhua lub hydrogen atom sib koom ib lub electron nrog ib lub Carbon atom.
- Cov pa roj carbon muaj plaub lub electrons nrog plaub lub Hydrogen atoms, ib qho rau txhua lub atom.
Cov qauv Lewis rau methane yog raws li nram no:
“
H
|
H – C – H
|
H
“
Cov pa roj carbon nyob hauv nruab nrab nrog plaub daim ntawv cog lus covalent rau plaub lub hydrogen atoms.
Lo lus nug thib 3
Txheeb xyuas cov qauv Lewis thiab cov duab molecular rau carbon dioxide (CO₂).
Kev Sib Tham:
Cov pa roj carbon dioxide muaj ib lub atom carbon (C) thiab ob lub atom oxygen (O).
1. Kev Teeb tsa Hluav Taws Xob:
- Cov pa roj carbon: 1s² 2s² 2p² (tag nrho 6 lub electrons)
– Cov pa oxygen: 1s² 2s² 2p⁴ (tag nrho 8 lub electrons)
Cov pa roj carbon muaj plaub lub electrons valence, thaum txhua lub atom oxygen muaj rau. Cov pa roj carbon xav tau plaub lub electrons ntxiv rau ib lub octet, thaum txhua lub atom oxygen xav tau ob lub ntxiv.
2. Kev Tsim Cov Kev Sib Koom Tes:
- Cov pa roj carbon sib koom ob lub electrons nrog txhua lub atom oxygen.
- Ob daim ntawv cog lus sib koom ua ke tau tsim ntawm Carbon thiab txhua Oxygen.
Cov qauv Lewis rau CO₂ yog raws li nram no:
“
O = C = O
“
Cov duab ntawm lub molecule yog linear nrog lub kaum sab xis ntawm 180 °.
Lo lus nug thib 4
Xam tag nrho cov electrons valence thiab kos ib lub qauv Lewis rau lub molecule ammonia (NH₃).
Kev Sib Tham:
Ammonia muaj ib qho nitrogen atom (N) thiab peb hydrogen atoms (H).
1. Kev Teeb tsa Hluav Taws Xob:
– Nitrogen: 1s² 2s² 2p³ (7 electrons tag nrho)
– Hydrogen: 1s¹ (tag nrho 1 electron)
Nitrogen muaj tsib lub electrons valence, xav tau peb lub electrons ntxiv rau ib qho octet.
2. Tag Nrho Cov Valence Electrons:
- Nitrogen: 5 valence electrons.
– Hydrogen (3 lub atoms): 3 lub electrons (1 lub electron ib lub atom).
Tag nrho cov electrons valence = 5 + 3 = 8 valence electrons.
3. Kev Tsim Cov Kev Sib Koom Tes:
- Nitrogen sib koom ib lub electron nrog txhua lub Hydrogen atom.
Tus qauv Lewis rau NH₃ yog:
“
H
|
H – N – H
|
“
Thiab ib khub ntawm cov electrons dawb (khub ib leeg) yog nyob rau hauv nitrogen.
Lo lus nug thib 5
Kos thiab piav qhia txog Lewis cov qauv rau nitrate ion (NO₃⁻).
Kev Sib Tham:
Cov nitrate ion yog ib qho polyatomic compound nrog ib qho nitrogen (N) thiab peb cov oxygens (O), thiab ib qho negative charge.
1. Kev Teeb tsa Hluav Taws Xob:
– Nitrogen: 1s² 2s² 2p³ (7 electrons tag nrho)
– Cov pa oxygen: 1s² 2s² 2p⁴ (tag nrho 8 lub electrons)
Nitrogen muaj tsib lub valence electrons, thaum txhua lub oxygen muaj rau lub valence electrons.
2. Tag Nrho Cov Valence Electrons:
- Nitrogen: 5 electrons.
– Oxygen (3 atoms): 18 electrons (6 electrons ib atom).
- Ntxiv vim yog cov ions tsis zoo: 1 electron.
Tag nrho cov electrons valence = 5 + 18 + 1 = 24 valence electrons.
3. Kev Tsim Cov Kev Sib Koom Tes thiab Kev Npaj Cov Qauv Lewis:
- Nitrogen tsim ob txoj kev sib txuas nrog ib qho ntawm cov pa oxygen thiab ib txoj kev sib txuas nrog ob lub pa oxygen.
- Qhov kev faib tawm ntawm cov nqi tsis zoo ntawm ob lub atoms oxygen nrog ib qho kev sib txuas ua ke cuam tshuam nrog resonance.
Tus qauv Lewis rau NO₃⁻ yog:
“
O
/
NYOB RAU = O
“
Tab sis yuav tsum ntxiv ib lub cim resonance los piav qhia txog electron delocalization.
Xaus
Kev sib txuas ntawm covalent yog lub tswv yim tseem ceeb hauv chemistry, qhov twg cov atoms sib koom cov electrons kom ua tiav qhov ruaj khov. Kev nkag siab txog yuav ua li cas kos Lewis cov qauv, suav cov valence electrons, thiab txiav txim siab cov duab molecular yog cov txuj ci tseem ceeb rau kev nkag siab tob dua txog cov txheej txheem tshuaj lom neeg. Los ntawm cov piv txwv saum toj no, nws vam tias cov nyeem ntawv yuav nkag siab zoo dua txog kev tsim thiab cov yam ntxwv ntawm cov kev sib txuas ntawm covalent.
