Ta yaya domin sanin valence

The kalmar "valence na" Latin harshe ( «valēns») da aka fassara a matsayin "da ciwon da karfi." A karo na farko shi ne aka ambata a cikin farkon karni na 15th, amma da darajar ( "miyagun ƙwayoyi" ko "tsantsa") da kõme ba yi da wani zamani fassarar. The kafa wannan mas'ala ta valence ne wani shahararren English sunadarai E. Frankland. Ya a 1852 da aka buga a takarda a cikin abin da aka reinterpreted duk theories kuma zaton cewa wanzu a wannan lokaci. Yana da aka Eduardom Franklendom gabatar da manufar "connective karfi", wanda ya zama tushen da rukunan valence, amma amsar tambayar "Ta yaya zan sami valence?" A wannan lokacin ya ba tukuna aka tsara.

Bugu da ari rawa wajen ci gaban ka'idar da aka buga ta da Friedrich Agusta Kekule (1857), Archibald Scott Cooper (1858), A. M. Butlerova (1861), A. von Hoffmann (1865). A 1866, F. A. Kekule a cikin littafi kawo sunayensu stereochemical model sinadaran kwayoyin da carbon zarra tetrahedral sanyi a cikin nau'i na zane, wanda ya zama bayyananne yadda za a ƙayyade da valency, msl, carbon.

Muhimmai na zamani ka'idar sinadaran bonding ne jimla-inji yi, ya nuna cewa jimlar electron biyu kafa ta hulda da biyu kwayoyin halitta. Kwayoyin zarra da unpaired electrons da layi daya spins, tare da antiparallel iya kafa na kowa electron biyu. A sunadarai bond kafa tsakanin biyu kwayoyin halitta kamar yadda suka kusanci, aka partially rufe da electron girgije. A sakamakon haka, tsakanin biyu tsakiya da aka kafa yawa na wutar lantarki, wanda aka janyo hankalin zuwa gaskiya ma cajin tsakiya da kuma kafa kwayoyin. Irin wannan misali na inji na hulda da daban-daban kwayoyin halitta underlies da sinadaran bond ka'idar Hanyar ko da wani valence bond. Saboda haka, bayan duk, da yadda za a ƙayyade da valence na? Wajibi ne a ƙayyade yawan shaidu cewa zarra iya nunawa. In ba haka ba, za ka iya ce cewa kana bukatar ka sami lambar na valence electrons.

Idan muka yi amfani da lokaci-lokaci tebur, yana da sauki mu fahimci yadda za a ƙayyade da valence na kashi bisa ga yawan electrons a cikin matsanancin harsashi zarra. Suna da ake kira valence. Duk da abubuwa a cikin kowane rukunin (shirya a ginshikan) a cikin matsanancin bawo da wannan yawan electrons. A na farko rukuni na abubuwa (H, Li, Na, K da sauransu) yana daya valence electron. Na biyu (Ka kasance, MG, Ca, Sr, kuma haka a) - biyu. A bisa uku (B, Al, Ga, da dai sauransu) - domin uku. A karo na hudu (C, Si, Ge, da dai sauransu) - hudu valence electrons. A karo na biyar kungiyar rabi (N, P, As, da dai sauransu) da biyar valence electrons. Za ka iya ci gaba da on, saboda shi ne bayyananne cewa yawan electrons a cikin matsanancin harsashi na electron girgije zai zama daidai da na lokaci-lokaci tebur rukunin lambar. Duk da haka, wannan riko ga na farko uku kungiyoyin na bakwai lokaci kuma su m, kuma ko da layuka (lokuta cikin sahu, kuma layuka na tebur). Tun da hudu lokacin da ta huɗu kungiyar (msl, Ti, ZR, HF, Ku) gefen abubuwa na subgroups da suke a ko da layuka ne a cikin matsanancin harsashi na yawan electrons, wasu fiye da kungiyar lambar.

A ra'ayi na "valence na" duk wannan lokaci ya halartar gagarumin canje-canje. A halin yanzu babu daidaita ko ta kimiyya fassarar. Saboda haka, ikon amsa tambaya "Ta yaya domin sanin valence?" Ne yawanci amfani ga methodological dalilai. Valence zaci ikon atoms shiga dauki da kwayoyin ta samar da sunadarai shaidu kira covalent. Saboda haka valence iya bayyana kawai da wani lamba.

Alal misali, yadda za a ƙayyade da valence na sulfur zarra a mahadi kamar hydrogen sulfide, ko sulfuric acid. Ga wani kwayoyin inda wani sulfur zarra ne bonded zuwa biyu hydrogen atoms, da valence na sulfur zuwa hydrogen zai zama daidai da biyu. A wani kwayoyin na sulfuric acid ta valence na oxygen ne shida. Kuma a gaskiya, a lokuta biyu da valence numerically daidai da cikakkar darajar da mataki na hadawan abu da iskar shaka da sulfur zarra a cikin wadannan sunadaran kwayoyin. Kamar yadda H2S kwayoyin ta digiri na hadawan abu da iskar shaka so -2 (tun da electron yawa daga cikin samuwar aka canja saboda da sulfur zarra, wanda shi ne mafi electronegative). A cikin kwayoyin na H2SO4 hadawan abu da iskar shaka yawan sulfur kwayoyin halitta ne daidai da shida (tun da electron yawa da aka canja zuwa mafi electronegative oxygen zarra).