Momwe mungadziwire valence

Mawu oti "Valence" ochokera ku Chilatini ("valēns") amatembenuzidwa ngati "kukhala ndi mphamvu". Anatchulidwa koyambirira kumayambiriro kwa zaka za zana la 15, koma tanthauzo lake ("mankhwala" kapena "kuchotsa") silinakhudze ndi kutanthauzira kwamakono. Woyambitsa lingaliro la tsopano la valence ndi katswiri wamakono wotchuka wa Chingerezi E. Frankland. Mu 1852 iye adafalitsa pepala limene malingaliro onse ndi malingaliro omwe analipo panthawiyo anali atakumbukiranso. Anali Edward Frankland amene adayambitsa lingaliro la "kugwirizanitsa", lomwe linakhala maziko a chiphunzitso cha valence, koma yankho la funso lakuti "Kodi mungapeze bwanji valence?" Pa nthawi imeneyo anali asanapangidwe.

Chinthu chinanso pakukula kwa chiphunzitsocho chinayesedwa ndi ntchito ya Friedrich August Kekule (1857), Archibald Scott Cooper (1858), A. Butlerov (1861), A. von Hofmann (1865). Ndipo m'chaka cha 1866 FA Kekule mu bukhu lake adapangitsa makompyuta a mitundu yosiyanasiyana ya mankhwala omwe ali ndi atomu ya mpweya wa mitsempha ya tetrahedral, monga momwe zidawonekera momveka bwino momwe mungagwiritsire ntchito valence monga mwa carbon.

Maziko a chiphunzitso chamakono cha kugwirizanitsa mankhwala ndi kuchuluka kwa mawonekedwe amodzi, omwe amatsimikizira kuti chifukwa cha kugwirizana kwa ma atomu awiri, magulu awiri a electron amapangidwa. Maatomu okhala ndi ma electron osayendayenda omwe ali ndi mawonekedwe ofanana omwe amatha kupanga mawonekedwe omwe amagwirizana. Mgwirizano wamagetsi pakati pa ma atomu awiri pamene iwo amayenderana wina ndi mzake ndi mtambo wochuluka wa electron. Chotsatira chake, pakati pa ziwirizi zimagwidwa ndi mphamvu zamagetsi, zomwe zimakhudzidwa kwambiri ndi nuclei, ndipo molekyu amapangidwa. Lingaliroli la njira yogwirizanirana kwa maatomu osiyanasiyana linapanga maziko a chigwirizano cha mankhwala kapena njira yogwirizanirana ndi valence. Kotero chimodzimodzi, momwe mungadziwire valence? Ndikofunika kudziwa chiwerengero cha mabungwe omwe atomu amatha kupanga. Apo ayi, tikhoza kunena kuti tikufunikira kupeza nambala ya ma electron.

Ngati tigwiritsa ntchito tebulo la periodic, n'zosavuta kumvetsetsa momwe tingadziwire valeni ya chinthucho ndi chiwerengero cha electron mu chigoba chapakati cha atomu. Iwo amatchedwa valence. Zinthu zonse mu gulu lirilonse (zomwe ziri muzitsulo) zili ndi nambala yomweyo ya magetsi m'zipolopolo zakunja. Zinthu za gulu loyamba (H, Li, Na, K ndi zina) zimakhala ndi electroni imodzi. Yachiwiri (Be, Mg, Ca, Sr, ndi zina zotero) ali ndi ziwiri. Wachitatu (B, Al, Ga ndi ena) - atatu. Wachinayi (C, Si, Ge ndi ena) ali ndi magetsi anayi a valence. Zinthu za gulu lachisanu (N, P, As ndi zina) zimakhala ndi ma electron asanu. Titha kupitirizabe, chifukwa ndizoonekeratu kuti chiwerengero cha electron m'kati mwa mtambo wa electron chidzakhala chofanana ndi chiwerengero cha gulu la tableodic. Komabe, izi zikuwonetsedwera kwa magulu atatu oyambirira a nthawi zonse zisanu ndi ziwiri ndi mndandanda wawo komanso wosamvetseka (nthawi ndi mndandanda uli m'mizere ya tebulo). Kuyambira pa nthawi yachinayi ndi gulu lachinayi (mwachitsanzo, Ti, Zr, Hf, Ku), zigawo za magulu ang'onoang'ono m'mizere ija zili ndi chiwerengero cha ma electron omwe amasiyanasiyana ndi nambala ya gulu.

Lingaliro la "valence" kwa nthawi yonseyi lasintha kwambiri. Pakalipano palibe kutanthauzira kwasayansi kapena kufanana kwake. Choncho, kuthekera kuyankha funso lakuti "Momwe mungasankhire valence?" Nthawi zambiri amagwiritsidwa ntchito pofuna njira. Valence imaonedwa kuti ndi yothetsera ma atomu, kuti apangitse mamolekyu okhala ndi zida zamagetsi, zomwe zimatchedwa zowonongeka. Choncho, valence ikhoza kuwonetsedwa kokha ndi nambala.

Mwachitsanzo, momwe mungadziwire valence ya atomu ya sulfure m'magulu monga hydrogen sulphide kapena sulfuric acid. Kwa kamolekyu komwe atomu ya sulfure imakhala ndi ma atomu awiri a haidrojeni, hydrogen valence ya hydrogen idzakhala iwiri. Mu sulfuric acid molecule, oxygen yake valence ndi zisanu ndi chimodzi. Muzochitika zonsezi, valence imagwirizana ndi chiwerengero cha mlingo wa okosijeni wa atomu ya sulfure mu mamolekyu awa. Mu molekyu ya H2S, dziko lake la okosijeni lidzakhala -2 (popeza kuchuluka kwa ma electron mu mapangidwe a mgwirizano kumasinthidwa ku atomu ya sulfa, yomwe ndi yosankhidwa pamphamvu kwambiri). Mu molecule H2SO4, mlingo wa okosijeni wa atomu ya sulfure ndi +6 (popeza mphamvu ya electron imasunthira ku atomu yochuluka ya electronegative atomu).