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Date: 28-12-2018
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Date: 29-11-2018
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Date: 20-12-2018
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Atomic spectra and flame tests
In the vapour state, the alkali metals exist as atoms or M2 molecules. The strength of the M_M covalent bond decreases down the group. Excitation of the outer ns1 electron of the M atom occurs easily and emission spectra are readily observed. We have already described the use of the sodium D-line in the emission spectrum of atomic Na for specific rotation measurements. When the salt of an alkali metal is treated with concentrated HCl (giving a volatile metal chloride) and is heated strongly in the non-luminous Bunsen flame, a characteristic flame colour is observed (Li, crimson; Na, yellow; K, lilac; Rb, red-violet; Cs, blue) and this flame test is used in qualitative analysis to identify the M ion. In quantitative analysis, use is made of the characteristic atomic spectrum in flame photometry or atomic absorption spectroscopy.
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تفوقت في الاختبار على الجميع.. فاكهة "خارقة" في عالم التغذية
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أمين عام أوبك: النفط الخام والغاز الطبيعي "هبة من الله"
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قسم شؤون المعارف ينظم دورة عن آليات عمل الفهارس الفنية للموسوعات والكتب لملاكاته
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