Isakhiwo se-athomu nama-isotope: kusuka ezimpawini ze-nuclide kuya esisindweni se-athomu

Ama-proton, ama-neutron nama-electron ngamayunithi alinganisiwe

I-proton iphethe ishaji engu-+1 ngamayunithi eshaji eyisisekelo, e = 1.602 × 10⁻¹⁹ C, kanti i-electron iphethe u-−1. I-neutron ayinayo ishaji. Izisindo ngokuvamile zinikezwa ngamayunithi esisindo se-athomu ahlanganisiwe (u, abizwa nangokuthi ama-dalton, Da), lapho u-1 u eyingxenye eyodwa kweziyishumi nambili zesisindo se-athomu ye-carbon-12, 1.6605 × 10⁻²⁷ kg.

Ngokwamanani e-CODATA ka-2022 ashicilelwe yi-NIST, i-proton ingu-1.007276 u, i-neutron ingu-1.008665 u kanti i-electron ingu-0.000549 u. I-proton isinda cishe izikhathi ezingu-1836 kune-electron, ngakho cishe sonke isisindo se-athomu sihlala ku-nucleus. I-nucleus nayo incane kakhulu: irediyasi yayo isezingeni elingu-10⁻¹⁵ m, kanti irediyasi ye-athomu isezingeni elingu-10⁻¹⁰ m. Ngakho ama-electron anquma usayizi we-athomu nekhemistri yayo, kanti i-nucleus inquma isisindo sayo.

Ukufunda izimpawu ze-nuclide nokubala izinhlayiya kuma-ayoni

Inombolo ye-athomu u-Z yinani lama-proton. Ichaza isakhi: yonke i-athomu enama-proton angu-17 iyi-chlorine. Inombolo yesisindo u-A yisamba sama-proton nama-neutron, ngakho inani lama-neutron lingu-A − Z. Uphawu lwe-nuclide lubhala u-A njenge-superscript ngakwesobunxele no-Z njenge-subscript ngakwesobunxele ophawini lwesakhi, njengaku-³⁵₁₇Cl. Ngoba uphawu seluvele lunquma u-Z, i-subscript ivame ukushiywa, kunikeze u-³⁵Cl noma i-chlorine-35.

Ama-electron alingana nama-proton kuphela ku-athomu engathathi hlangothi. I-ayoni enoshaji q inama-electron angu-Z − q, ngakho ishaji eyakhayo isho ama-electron ambalwa kanti ishaji engelihle isho amaningi. Ishaji ayilokothi ishintshe i-nucleus.

Isibonelo esisebenzile 1. Ku-⁵⁶Fe³⁺: Z = 26, ngakho ama-proton angu-26; 56 − 26 = ama-neutron angu-30; 26 − 3 = ama-electron angu-23. Ku-¹²⁷I⁻: ama-proton angu-53, 127 − 53 = ama-neutron angu-74 kanye no-53 + 1 = ama-electron angu-54. Ku-³⁴S²⁻: ama-proton angu-16, ama-neutron angu-18 nama-electron angu-18. Qaphela ukuthi u-³⁴S²⁻ unenani lama-electron elifana nele-athomu ye-argon; amanani alinganayo ama-electron yiwo enza ama-ayoni abe yi-isoelectronic, hhayi izinombolo zesisindo ezilinganayo.

Kungani ama-isotope esabela ngokufanayo kodwa ehlukile ngesisindo

Ama-isotope angama-athomu ano-Z ofanayo kodwa anamanani ahlukene ama-neutron. I-chlorine-35 ne-chlorine-37 zombili zinama-proton angu-17 futhi, njengama-athomu angathathi hlangothi, nama-electron angu-17. Ukuziphatha kwamakhemikhali kulawulwa ama-electron, ngakho la ma-isotope amabili akha izinhlanganisela ezifanayo ngezilinganiso ezifanayo.

Izakhiwo ezincike esisindweni ziyahluka kancane. Amamolekyuli alula ahamba ngokushesha ezingeni lokushisa elithile, futhi izibopho kuma-isotope asindayo zisabela kancane kancane. Le mithelela incane ezakhini ezisindayo. Ukunothisa i-uranium kukhombisa ukuthi incane kangakanani. Ngokomthetho ka-Graham, amazinga e-effusion ka-²³⁵UF₆ no-²³⁸UF₆ asesilinganisweni esingu-√(M₂/M₁). Usebenzisa izisindo ze-isotope ze-NIST, M(²³⁵UF₆) = 349.034 g/mol no-M(²³⁸UF₆) = 352.041 g/mol, ngakho isilinganiso singu-√(352.041/349.034) = 1.0043. Ukudlula okukodwa ngesithiyo kunothisa i-isotope elula ngaphansi kwengxenye yephesenti, yingakho izitshalo zokunothisa zidinga izigaba eziningi ezilandelanayo.

Izilinganiso ezinesisindo: kusuka ezisindweni ze-isotope kuya esisindweni se-athomu

Isisindo se-athomu ethebuleni lezikhathi akusona isisindo sanoma iyiphi i-athomu eyodwa. Siyisisindo esimaphakathi sama-athomu esakhi esampuleni evamile, esinesisindo ngokuthi i-isotope ngayinye ivame kangakanani. Phindaphinda isisindo se-isotope ngayinye ngokuchichima kwayo okuyingxenye bese wengeza imikhiqizo. Izingxenye kufanele zihlangane zibe ngu-1.

Isibonelo esisebenzile 2. I-magnesium inama-isotope amathathu azinzile. Kusuka kumatafula e-NIST e-Atomic Weights and Isotopic Compositions: ²⁴Mg, 23.985042 u, ukuchichima 0.7899; ²⁵Mg, 24.985837 u, 0.1000; ²⁶Mg, 25.982593 u, 0.1101. Imikhiqizo ingu-18.94578, 2.49858 no-2.86068 u, futhi isamba sayo singu-24.30505 u. Imithetho eqinile yezinombolo ezibalulekile esetshenziswe ekuchichimeni okunezinombolo ezine ibizokuyisa lokhu ku-24.31 u. Uma kugcinwe ezindaweni ezintathu zedesimali, kungu-24.305 u, inani elivamile eliphrintwe emathebulini amaningi ezikhathi.

Yenza ukubala okufanayo nge-chlorine, usebenzisa u-³⁵Cl ku-34.968853 u nokuchichima okungu-0.7576 no-³⁷Cl ku-36.965903 u no-0.2424: 26.4924 + 8.9605 = 35.453 u. Ukulinganisela okusheshayo kubamba amaphutha: isilinganiso kufanele sibe phakathi kwezisindo ze-isotope futhi sisondele kakhulu kuleyo echichimayo kakhulu.

Ukusebenza uhlehla ukuthola ukuchichima kwe-isotope

Uma isakhi sinama-isotope amabili futhi wazi isisindo se-athomu, ungakuxazulula ukuchichima. Biza ingxenye ye-isotope yokuqala ngo-x; eyesibili-ke ingu-1 − x. Bhala isilinganiso esinesisindo njengesibalo bese uxazulula u-x.

Isibonelo esisebenzile 3. I-copper inesisindo se-athomu esijwayelekile esingu-63.546 nama-isotope amabili azinzile, u-⁶³Cu ku-62.929598 u no-⁶⁵Cu ku-64.927790 u (NIST). Bese 62.929598x + 64.927790(1 − x) = 63.546. Ukuhlela kabusha kunikeza x = (64.927790 − 63.546)/(64.927790 − 62.929598) = 1.381790/1.998192 = 0.6915. Ngakho i-copper ingu-69.15% ⁶³Cu no-30.85% ⁶⁵Cu, okuphinda ukuchichima kwe-NIST okungu-0.6915 no-0.3085.

Le ndlela isebenza kuphela kuma-isotope amabili. Uma kunamathathu, isilinganiso esisodwa sinikeza isibalo esisodwa esinezinto ezimbili ezingaziwa, futhi udinga esinye isilinganiso, njenge-mass spectrum.

Amaphethini e-isotope ku-mass spectrum

I-mass spectrometer yenza isampula ibe ama-ayoni, ihlukanise ama-ayoni ngesilinganiso sesisindo neshaji, futhi irekhode ukuthi mangaki afika enanini ngalinye. Esakhini esisodwa, ukuphakama kweziqongo kunikeza ukuchichima kwama-isotope ngqo. Kumamolekyuli, ama-isotope ayahlangana futhi akhiqize amaphethini abonakalayo.

Isibonelo esisebenzile 4. Bikezela iphethini ye-molecular-ion ka-Cl₂. Vumela p = 0.7576 ku-³⁵Cl no-q = 0.2424 ku-³⁷Cl. Imolekyuli ingu-³⁵Cl–³⁵Cl (isisindo 70) ngamathuba angu-p² = 0.5740, ³⁵Cl–³⁷Cl (isisindo 72) ngamathuba angu-2pq = 0.3673, no-³⁷Cl–³⁷Cl (isisindo 74) ngamathuba angu-q² = 0.0588. Isici esingu-2 sibala izindlela ezimbili zokuthola eyodwa yohlobo ngalunye. Uma kulinganiswe ukuze isiqongo eside kakhulu sibe ngu-100, iphethini ingu-100 : 64.0 : 10.2.

Izindlela ezimfushane ezimbili ziyalandela. Inhlanganisela ene-athomu eyodwa ye-chlorine ikhombisa iziqongo ezihlukene ngamayunithi esisindo amabili ngesilinganiso esicishe sibe ngu-3 : 1, ngoba p/q = 3.13. Inhlanganisela ene-athomu eyodwa ye-bromine ikhombisa iziqongo ezimbili ezicishe zibe nokuphakama okulinganayo, ngoba i-NIST ibhala u-⁷⁹Br ku-0.5069 no-⁸¹Br ku-0.4931.

Amaphutha esakhiwo se-athomu alahlekisa ngamamaki

Amaphutha amaningi avela ekuxubeni amanani amathathu noma ekuthatheni isisindo se-athomu njengesakhiwo se-athomu eyodwa. Bhala u-Z, u-A neshaji ngaphambi kokuthi ubale noma yini.

• Ukushintsha inani lama-proton ukuze kwenziwe i-ayoni. Ishaji ishintsha ama-electron kuphela; ama-proton anquma isakhi.
• Ukwengeza ama-electron e-ayoni eyakhayo. I-ayoni engu-3+ inama-electron ambalwa ngamathathu kune-athomu.
• Ukufunda isisindo se-athomu njengenombolo yesisindo. Ayikho i-athomu ye-chlorine enesisindo esingu-35.45 u; siyisilinganiso sama-athomu acishe abe ngu-35 u no-37 u.
• Ukusebenzisa amaphesenti njengezingxenye ngaphandle kokuhlukanisa ngo-100, okunikeza isilinganiso esikhulu ngokuphindwe izikhathi ezingu-100.
• Ukukhohlwa isici esingu-2 samabhangqa ama-isotope axubile, njengo-³⁵Cl–³⁷Cl, lapho ubikezela i-mass spectrum.
• Ukubiza ama-nuclide amabili ngokuthi ama-isotope ngoba anenombolo yesisindo efanayo. U-¹⁴C no-¹⁴N babelana ngo-A kodwa bayizakhi ezihlukene.

I-mass defect nezisindo ze-athomu ezinikezwa njengebanga

Ukwengeza ama-proton ayisithupha, ama-neutron ayisithupha nama-electron ayisithupha ngezisindo ze-CODATA kunikeza u-12.0989 u, kodwa i-athomu ye-carbon-12 ingu-12 u ncamashi. U-0.0989 u olahlekile, cishe u-0.82% wesamba, uhambisana namandla akhululwa lapho i-nucleus yakheka. Le mass defect yiyo eyenza izisindo ze-isotope zingabi izinombolo eziphelele, futhi iyisiqalo samandla okubopha enyukliya.

Kwezinye izakhi, ingxube yama-isotope iyahluka ngokwanele phakathi kwemithombo yemvelo kangangokuthi iKhomishana ye-IUPAC Yokuchichima Kwama-isotope Nezisindo Ze-athomu ibika ibanga esikhundleni senombolo eyodwa. I-chlorine ibhalwe njengo-[35.446, 35.457] ne-magnesium njengo-[24.304, 24.307]. Ezibalweni ezijwayelekile, sebenzisa amanani awodwa avamile, 35.45 no-24.305, ngaphandle uma isifundo sakho sisho okunye.