Txiav txim siab txog kev siv tshuaj ntawm kev tshuaj

Cov theem ntawm kev paub ntawm cov qauv hauv tsev thiab cov khoom xyaw hauv lub XIX xyoo pua tsis pub peb piav qhia qhov laj thawj uas yog vim li cas cov xaim hluav taws tsim ib co xov tooj nrog lwm cov khoom. Tab sis cov tswv yim ntawm cov kws tshawb fawb tau nthuav tawm lawv lub sij hawm, thiab tseem muaj kev kawm ua ib qho ntawm cov qauv hauv paus chemistry.

Los ntawm keeb kwm ntawm lub tswvyim ntawm "lub valence ntawm tshuaj tshuaj"

Lub Koom Txoos hais lus Askiv ntawm lub xyoo pua puv 19, Edward Frankland, tau qhia lub sij hawm "kev txuas" rau kev siv kev piav qhia txog kev sib cuam tshuam ntawm atoms nrog txhua lwm yam. Tus kws tshawb fawb pom tias qee cov tshuaj tiv thaiv kev sib xyaw nrog cov zauv ntawm lwm tus. Piv txwv, nitrogen ntxiv peb qhov atoms hydrogen rau ammonia lub cev.

Thaum lub Tsib Hlis Ntuj xyoo 1852, Frankland tau pom zoo tias muaj qee cov kev sib raug zoo ntawm cov chemical uas yog ib qho atom uas muaj peev xwm ua tau nrog lwm yam me me. Frankland siv lo lus "sib txuas lus" los piav txog dab tsi yuav tom qab raug hu ua tus neeg muaj hmoo. Cov kws tshuaj British tau tsim muaj ntau txoj hlua sib txuas ua ke ntawm cov tib neeg cov ntsiab lus tau paub nyob nruab nrab ntawm XIX xyoo pua. Lub chaw ua hauj lwm ntawm Frankland tau dhau los ua ib qho tseem ceeb hauv kev ua qauv niaj hnub.

Kev loj hlob ntawm kev pom

German chemist F.A. Kekule ua pov thawj hauv 1857 tias cov roj yog plaub-puag. Hauv nws txoj kev simplest - methane - muaj cov kev sib txuas nrog 4 atoms hydrogen. Lo lus "basicity" tus kws tshawb fawb tau siv los txheeb xyuas cov khoom ntawm cov ntsiab lus kom muab ib tug zauv uas txhais hais meej. Nyob rau hauv Russia, cov ntaub ntawv nyob rau hauv cov qauv ntawm cov teeb meem systematized A. M. Butlerov (1861). Ntxiv kev txhim kho ntawm txoj kev xav ntawm kev sib tsoo tshuaj yog vim qhov kev xav ntawm periodic hloov nyob rau hauv cov khoom ntawm cov ntsiab lus. Nws sau - lwm zoo heev Lavxias teb sab chemist D. I. Mendeleev. Nws ua pov thawj tias qhov kev siv tshuaj ntawm cov chemical cov ntsiab lus hauv cov khoom sib txuas thiab lwm cov khoom yog vim los ntawm txoj hauj lwm uas lawv nyob hauv lub caij ua haujlwm.

Teeb duab sawv cev ntawm kev muaj nuj nqis thiab kev siv tshuaj lom neeg

Qhov tseem ceeb ntawm kev tsim qauv ntawm molecules yog ib qho ntawm cov ntsiab lus tsis tshua muaj txiaj ntsig ntawm txoj kev xav qhov kev xav. Tus thawj qauv nyob rau hauv 1860, thiab txij thaum 1864 tau raug siv yam ntxwv qauv sawv cev tshuaj circumferential cim hauv. Ntawm cim khiav ceev atoms denoted tshuaj daim ntawv cog lus, thiab tus naj npawb ntawm kab yog sib npaug zos rau cov valence. Nyob rau tib lub xyoo, thawj pob-thiab-rod qauv tau tsim (saib daim duab ntawm sab laug). Nyob rau hauv 1866, Kekule npaj tau ib daim duab stereochemical ntawm cov roj atom nyob rau hauv daim ntawv ntawm ib tug tetrahedron, uas nws muaj nyob hauv nws phau ntawv "Organic Chemistry."

Valence ntawm cov tshuaj hais, thiab cov emergence ntawm kev sib raug zoo kawm los ntawm G. Lewis, uas luam tawm nws tej hauj lwm nyob rau hauv 1923 tom qab lub foundations ntawm cov electron. Qhov kev sibtham tsis muaj kev txwv me me, uas yog ib feem ntawm lub cev ntawm atoms, raug hu ua. Nyob rau hauv nws phau ntawv, Lewis siv cov ntsiab lus nyob ntawm plaub sab ntawm lub cim ntawm ib qho tshuaj ua kom pom cov khoom siv electrons.

Valence rau hydrogen thiab cov pa

Ua ntej lub creation ntawm lub periodic system ntawm valence ntawm cov tshuaj hais nyob rau hauv lub tebchaw twb ua los sib piv nrog rau cov atoms uas nws yog lub npe hu. Raws li cov qauv, hydrogen thiab oxygen raug xaiv. Lwm cov keeb tshuaj lom los yog hloov tus nab npawb H thiab O.

Nyob rau hauv no txoj kev, cov khoom tau txiav txim siab hauv cov compounds nrog monovalent hydrogen (lub ntsiab lus ntawm lub thib ob lub ntsiab lus yog muab los ntawm Roman numeral):

• HCl - chloro (kuv):
• H ₂ O - oxygen (II);
• NH ₃ - nitrogen (III);
• CH ₄ - carbon (IV).

Lub oxides ntawm K ₂ O, CO, N ₂ O _3, SiO _2, li ₃ tau txiav txim los ntawm lub valence ntawm hlau thiab nonmetals oxygen, doubling tus xov tooj ntawm atoms attachable O. tau nram qab no tseem ceeb: K (I), C ( II), N (III) , Si (IV), S (VI).

Yuav ua li cas los txiav txim siab lub valence ntawm tshuaj ntsiab lus

Muaj cov kev tu ncua hauv kev tsim cov tshuaj qoob loo uas muaj ntau cov khoom sib koom tes:

• Qhov kev hloov ntawm hydrogen yog kuv.
• Cov pa oxygen li qub yog II.
• Rau cov ntsiab lus uas tsis yog cwj pwm, cov nqi qis dua tuaj yeem txiav txim siab los ntawm cov qauv mis 8 - pes tsawg tus pab pawg uas lawv tau nyob rau hauv lub rooj xaib. Ntau dua, yog tias ua tau, txiav txim siab los ntawm pawg naj npawb.
• Rau cov ntsiab lus ntawm cov pawg neeg tsawg, qhov siab tshaj plaws qhov kev muaj peev xwm yog qhov sib npaug ntawm cov pawg hauv cov txheej txheem.

Kev txiav txim siab ntawm kev siv tshuaj ntawm cov tshuaj chemical los ntawm formula ntawm cov compound yog nqa tawm raws li siv cov lus qhia nram qab no:

1. Sau rau saum toj ntawm cov tshuaj kos npe rau ib qho kev paub meej rau ib qho ntawm cov ntsiab lus. Piv txwv li, nyob rau hauv Mn ₂ O ₇ oxygen valency yog II.
2. Xam tag nrho tus nqi, uas nws yog qhov tsim nyog yuav tau muab cov txiaj ntsim los ntawm tus naj npawb ntawm cov xaim hluav taws xob hauv tib lub tshuaj molecule: 2 * 7 = 14.
3. Txiav txim siab qhov kev muaj nuj nqis ntawm ob lub ntsiab lus uas nws tsis paub. Faib tus nqi tau txais nyob hauv nqe 2 los ntawm tus naj npawb ntawm Mn atoms nyob rau hauv molecule.
4. 14: 2 = 7. Lub ntsiab lus ntawm manganese hauv nws cov oxide siab dua yog VII.

Qhov tseem ceeb thiab qhov tsis sib haum xeeb

Qhov tseem ceeb rau hydrogen thiab oxygen yog txawv. Piv txwv li, sulfur nyob rau hauv lub chaw tub rog ntawm H ₂ S yog divalent, raws li nyob rau hauv cov mis mos li ₃ - hexavalent. Cov pa roj carbon monoxide reacts nrog rau oxygen, CO thiab CO ₂ dioxide. Nyob hauv thawj qhov compound, qhov kev muaj nqis ntawm C yog II, thiab hauv ob, IV. Cov tib tus nqi nyob hauv methane CH _4.

Feem ntau cov ntsiab lus tsis pom ib qho, tab sis kuj tsis tshua muaj nqes, piv txwv, phosphorus, nitrogen, sulphur. Kev tshawb nrhiav qhov tseem ceeb ntawm qhov tshwm sim no tau tshwm sim rau qhov tshwm sim ntawm theories ntawm kev sib txuas tshuaj, cov tswv yim hais txog lub plhaub ntawm lub electron, molecular orbitals. Lub neej ntawm ntau qhov tseem ceeb ntawm tib qho khoom tau raug piav qhia raws li cov qauv ntawm cov xaim hluav taws xob thiab cov xaim hluav taws xob.

Cov ntsiab lus niaj hnub ntawm valence

Tag nrho cov atoms muaj xws li ib tus zoo nucleus surrounded los ntawm kev tsis pom zoo electrons. Lub plhaub txheej, uas lawv tsim, tsis tiav. Tus qauv tiav yog qhov tseem ruaj khov, nws muaj 8 electrons (octet). Cov tsos mob ntawm cov tshuaj lom neeg vim yog cov khoob khoob electronically ua rau lub zog ntawm lub ntiaj teb ua haujlwm zoo.

Txoj cai rau qhov kev tsim ntawm cov tebchaw yog kawm tiav ntawm lub plhaub los ntawm kev siv cov electron los yog muab tawm cov neeg tsis muaj hnub nyoog, nyob ntawm qhov txheej txheem ua hla yooj yim dua. Yog hais tias ib qho me me muab cov khoom tsis zoo rau qhov tsim kom muaj kev sib cog khoob, uas tsis muaj ib khub, ces nws cov ntaub ntawv muaj ntau txoj hlua vim muaj cov tsis muaj lub electrons. Raws li cov ntsiab lus niaj hnub no, lub ntsiab ntawm kev siv tshuaj atoms of chemical elements yog rab peev xwm los tsim ib lub xov tooj ntawm cov ntawv cog lus. Piv txwv li, nyob rau hauv lub molecule, H ₂ S leej faj, hydrogen sulfide acquires valence II (-), vim hais tias txhua atom koom nyob rau hauv lub tsim ntawm ob electron officers. Qhov kos npe "-" qhia tias qhov attraction ntawm electron pair rau ntau lub caij electronegative. Thaum tsawg electronegative rau nqi valence, ntxiv "+".

Nrog rau kev pub dawb-tswv yim mechanism, cov khoom sib koom tes ntawm ib lub caij thiab dawb valence orbitals ntawm qhov sib koom ua ke.

Ntsib ntawm qhov kev txheeb rau ntawm tus qauv ntawm lub cev

Xav txog, piv txwv li, cov pa roj carbon thiab oxygen, yuav ua li cas lub txiaj ntsim ntawm tshuaj muaj zog nyob ntawm cov qauv ntawm cov khoom. Mendeleyev lub rooj muab ib lub tswv yim ntawm cov yeeb yam tseem ceeb ntawm cov roj atom:

• Tshuaj sau tshuaj - C;
• Elementary tus xov tooj yog 6;
• Qhov nqi ntawm lub keeb tawm yog +6;
• Protons nyob rau hauv lub nucleus - 6;
• Electrons - 6, nrog rau 4 sab nraud, 2 ntawm daim ntawv no ib khub, 2 - unpaired ones.

Yog tias cov pa roj carbon atom hauv CO monooxide cov ntaub ntawv ob daim ntawv cog lus, tsuas yog 6 tsis pom hais tias nws siv. Yuav kom tau txais ib qho octet, nws yog ib qhov tsim nyog uas cov khub tsim 4 sab nraud tsis zoo. Cov roj carbon monoxide muaj valence IV (+) hauv dioxide thiab IV (-) hauv methane.

Cov xov tooj ntawm cov pa oxygen yog 8, lub plhaub npog muaj rau 6 electrons, 2 ntawm cov uas tsis tsim ib khub thiab koom nrog ua tshuaj lom neeg thiab koom nrog lwm cov qhov atoms. Lub txiaj ntsig oxygen nqi yog II (-).

Valence thiab oxidation xeev

Nyob rau hauv ntau ntau nws yog yooj yim dua siv lub sij hawm "oxidation lub xeev". Qhov no yog lub npe rau lub luag hauj lwm ntawm lub atom, uas nws xav tau yog tias tag nrho cov thwj toob khib electrons raug xa mus rau ib lub caij uas muaj nuj nqi ntau dua ntawm electronegativity (EO). Cov naj npawb oxidizing hauv cov khoom yooj yim yog xoom. Mus rau qhov degree ntawm oxidation ntau tshaj li cov EO ntawm lub caij ntxiv rau lub kos npe "-", electronegative tsis tshua muaj - "+". Piv txwv, rau cov hlau ntawm cov pawg hauv txhua pawg, oxidation degrees thiab ion nqi yog sib npaug ntawm cov pawg tsawg nrog cov cim "+". Feem ntau, qhov kev muaj nuj nqi thiab cov degree ntawm oxidation ntawm atoms nyob rau hauv tib chav kawm yog ntau qhov sib xws. Tsuas yog thaum muaj kev sib tshuam nrog ntau lub tshuab hluav taws xob (electronegative atoms) yog qhov degree ntawm oxidation zoo, nrog cov ntsiab lus rau EO tsawg dua, yog qhov tsis zoo. Lub tswvyim ntawm "valency" feem ntau tsuas yog siv rau cov khoom ntawm molecular qauv.