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Date: 28-1-2018
1247
Date: 22-11-2018
1128
Date: 11-1-2019
710
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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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علامات بسيطة في جسدك قد تنذر بمرض "قاتل"
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أول صور ثلاثية الأبعاد للغدة الزعترية البشرية
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مكتبة أمّ البنين النسويّة تصدر العدد 212 من مجلّة رياض الزهراء (عليها السلام)
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