Fahimtar Haɗin kai da Misalai
Pendahuluan
A fannin ilmin sunadarai, yadda kwayoyin halitta ke haɗuwa don samar da wani abu galibi yana ƙayyade halayen wannan abu. Wani muhimmin ra'ayi wanda ke bayyana yadda haɗin kwayoyin halitta yake da alaƙa. Haɗin Covalent (covalence) galibi ana samunsa a cikin mahaɗan da suka ƙunshi abubuwan da ba na ƙarfe ba, misali a cikin ruwa (H₂O), carbon dioxide (CO₂), methane (CH₄), da mahaɗan halitta daban-daban waɗanda sune tushen rayuwa. Fahimtar ma'anar covalence da misalai zasu taimaka mana mu fahimci yadda ake samar da tsarin kwayoyin halitta, dalilin da yasa wani abu ya... wurin tafasa wasu sinadarai, dalilin da yasa wasu sinadarai ke narkewa cikin sauƙi a cikin ruwa, da kuma yadda sinadaran ke faruwa.
Fahimtar Haɗin kai
Covalence ra'ayi ne da ya shafi samuwar covalent bonds, waɗanda sune haɗin sinadarai da ke faruwa lokacin da atoms biyu suka raba biyu na electrons don cimma daidaito. Gabaɗaya, atoms suna son cimma daidaiton electrons mai ƙarfi kamar iskar gas mai daraja (ƙa'idar octet), wanda ke nufin samun electrons 8 a cikin mafi kyawun harsashinsa (kodayake akwai wasu keɓancewa). Saboda ƙwayoyin halitta marasa ƙarfe suna da yawan electronegativities kuma ba su da sauƙin rasa electrons, hanya mafi yuwuwa don cimma daidaito ita ce ta hanyar raba electrons, maimakon ba da su ko karɓar su gaba ɗaya kamar yadda yake a cikin haɗin ionic.
A wata ma'anar, yayin da a cikin haɗin ionic, ana canja wurin electrons daga zarra ɗaya zuwa wani, a cikin haɗin covalent, ana raba electrons. Haɗin electrons ɗin da aka raba suna samar da haɗin electron guda biyu, wanda ke "haɗa" ƙwayoyin atomic guda biyu tare don samar da ƙwayar halitta ɗaya ko haɗin covalent.
Me yasa Haɗin Covalent ke Faruwa?
Haɗin covalent yana faruwa ne saboda ƙoƙarin isa ga ƙarancin yanayin kuzari mai ƙarfi. Lokacin da ƙwayoyin halitta biyu suka kusanci juna, electrons na valenance Ana iya amfani da su tare ta yadda kowace kwayar zarra ta bayyana tana da isasshen adadin electrons a cikin harsashin waje. Wannan yana sa tsarin ya fi karko fiye da lokacin da kwayoyin zarra ke tsaye su kaɗai.
Misali, kwayar halittar hydrogen (H) tana da electron guda ɗaya kuma tana son cimma daidaito kamar helium (He) tare da electrons guda biyu. Kwayoyin halittar hydrogen guda biyu na iya raba electrons guda biyu, suna samar da kwayar halittar H₂ . Kowace kwayar halittar H₂ yanzu tana "jin" kamar tana da electrons guda biyu a cikin harsashinta na farko, don haka tana samun daidaito.
Nau'ikan Hadin Covalent
Ana iya bambanta haɗin covalent bisa ga adadin nau'ikan lantarki da aka raba kuma bisa ga bambancin electronegativity tsakanin atoms.
1. Dangane da adadin nau'ikan lantarki da aka raba
1. Haɗin covalent guda ɗaya: raba nau'i 1 na electrons.
Misali: H—H a cikin H₂, ko C—H a cikin CH₄.
2. Haɗin covalent guda biyu: raba nau'i biyu na electrons.
Misali: O=O a cikin O₂, ko C=O a cikin CO₂.
3. Haɗin covalent guda uku: raba nau'i-nau'i 3 na electrons.
Misali: N≡N akan N₂.
Da yawan nau'ikan electrons da aka raba, haɗin zai fi ƙarfi kuma ya fi guntu nesa tsakanin atoms.
2. Dangane da bambancin ra'ayi
1. Haɗin covalent mara polar
Yana faruwa ne lokacin da dukkan ƙwayoyin halitta guda biyu suna da electronegativities iri ɗaya ko iri ɗaya, ta yadda za a raba nau'in electron ɗin daidai gwargwado.
Misali: H₂, O₂, N₂, Cl₂.
2. Haɗin haɗin gwiwa na polar
Wannan yana faruwa ne lokacin da bambancin electronegativity ya isa ya sa nau'in electron ɗin ya fi jan hankali zuwa ga ɗaya daga cikin atom ɗin. Wannan yana haifar da caji na ɓangare (δ⁺ da δ⁻).
Misalai: H—Cl a cikin HCl, O—H a cikin H₂O.
Yana da mahimmanci a bambanta cewa haɗin polar ba koyaushe yana nufin cewa molecule yana da polar ba; siffar molecule (geometry) yana tasiri ga polarity na molecule.
Misalan Haɗin gwiwa a cikin Abubuwan da ke Cikin Kullum
Ga wasu misalai da suke da sauƙin samu a rayuwar yau da kullum:
1. Ruwa (H₂O)
Ruwa muhimmin misali ne na wani abu mai haɗin gwiwa na polar covalent. Atom ɗin iskar oxygen ya fi hydrogen electronegative, don haka ɗayan biyun ya fi jan hankalin iskar oxygen. Wannan yana ba ruwa halaye na musamman kamar ikonsa na narkar da abubuwa da yawa, matsin lamba mai yawa a saman, da kuma zafin tafasa mai yawa idan aka kwatanta da sauran ƙananan ƙwayoyin halitta.
A cikin H₂O, akwai haɗin O—H guda biyu na polar. Bugu da ƙari, siffar "lanƙwasa" (ba layi ba) na ƙwayoyin ruwa yana nufin cewa lokutan dipole ɗinsu ba sa soke juna, don haka ƙwayoyin ruwa gaba ɗaya su kasance polar.
2. Carbon dioxide (CO₂)
CO₂ yana da haɗin covalent guda biyu tsakanin C da O (O=C=O). Haɗin C=O yana da polar, amma CO₂ layi ne, don haka lokutan dipole guda biyu suna share juna. Sakamakon haka, kwayar CO₂ ba ta da polar gaba ɗaya. Wannan shine dalili ɗaya da ya sa CO₂ ba ya narkewa sosai a cikin ruwa fiye da sinadarai masu tsarki na polar, kodayake har yanzu yana iya amsawa don samar da carbonic acid a ƙarƙashin wasu yanayi.
3. Methane (CH₄)
Methane shine mahaɗan halitta Kwayar halitta mai sauƙi wadda ta ƙunshi haɗin covalent guda ɗaya tsakanin C da H. Gabaɗaya, CH₄ ba ta da polar saboda siffarta tana da daidaiton tetrahedral kuma bambancin electronegativity tsakanin C da H bai yi yawa ba. Methane shine babban ɓangaren iskar gas kuma ana amfani da shi sosai a matsayin mai.
4. Iskar Oxygen (O₂) da Nitrogen (N₂)
O₂ yana da haɗin covalent guda biyu (O=O), yayin da N₂ yana da haɗin covalent guda uku (N≡N). Haɗin uku a cikin N₂ yana da ƙarfi sosai, wanda hakan ya sa nitrogen ba ya yin aiki da sauri (ba ya yin aiki da sauri) a ƙarƙashin yanayi na yau da kullun. Wannan shine dalilin da ya sa nitrogen ke mamaye sararin samaniyar Duniya amma ba ya yin aiki da sauƙi ba tare da yanayi na musamman ko taimakon mai kara kuzari ba.
5. Hydrogen chloride (HCl)
HCl misali ne na haɗin haɗin gwiwa na polar. Chlorine (Cl) ya fi hydrogen electronegative, don haka electrons ɗinsa suna jan hankali zuwa Cl, wanda ke haifar da caji na ɗan lokaci. Idan aka narkar da shi a cikin ruwa, HCl yana yin ionize don samar da H⁺ da Cl⁻, wanda hakan ya sa aka san shi da acid mai ƙarfi. Wannan yana nuna cewa mahaɗin zai iya samun haɗin gwiwa na covalent amma yana samar da ions a cikin ruwan.
6. Ammoniya (NH₃)
Ammonia tana da alaƙa mai ƙarfi tsakanin N da H. Kwayoyin halittar NH₃ suna da siffar trigonal pyramidal kuma suna da polar. Ana amfani da Ammonia sosai a masana'antar taki, tsaftacewa, da kuma hanyoyin sinadarai daban-daban. Polarity na Ammonia yana ba ta damar yin mu'amala sosai da ruwa.
Halaye na Gabaɗaya na Haɗaɗɗun Haɗaɗɗun Haɗaɗɗu
Gabaɗaya, mahaɗan covalent suna da halaye masu zuwa (kodayake akwai keɓancewa):
1. Da yawa daga abubuwan da ba na ƙarfe ba ne aka samar da su.
2. Gabaɗaya suna da ƙananan wuraren narkewa da tafasa fiye da mahaɗan ionic, musamman ga ƙananan ƙwayoyin halitta.
3. Haɗaɗɗun covalent marasa polar ba sa narkewa a cikin ruwa, amma suna narkewa a cikin abubuwan narkewa marasa polar.
4. Kada a yi amfani da wutar lantarki a yanayin da ba shi da ƙarfi; wasu na iya gudanar da wutar lantarki idan an haɗa su da ion a cikin ruwan (misali HCl a cikin ruwa).
5. Sau da yawa ana samunsa a cikin mahaɗan halitta kamar su hydrocarbons, alcohols, organic acids, da proteins.
Penutup
Covalence wani muhimmin ra'ayi ne da ke bayyana yadda atoms, musamman wadanda ba na ƙarfe ba, ke samar da haɗin gwiwa ta hanyar raba nau'ikan electron. Covalent bonds na iya zama guda ɗaya, ninki biyu, ko uku, kuma suna iya zama polar ko nonpolar. Misalan sun saba da rayuwar yau da kullun, kamar ruwa (H₂O), carbon dioxide (CO₂), methane (CH₄), oxygen (O₂), nitrogen (N₂), da hydrogen chloride (HCl). Ta hanyar fahimtar ma'anar covalence da misalai, za mu iya haɗa tsarin kwayoyin halitta cikin sauƙi tare da halayen zahiri da sinadarai na wani abu.
Idan kuna so, zan iya ƙara sigar kimiyya ta labarin (tare da tattaunawa kan tsarin Lewis, ƙa'idar octet, da tsarin kwayoyin halitta) ko kuma sigar da ta fi sauƙi ga ɗaliban makarantar sakandare.
