Nitrogen-Sulfur-Fluorine Ions

R. Mews, Nitrogen-Sulfur-Fluorine Ions, Adv. Inorg. Chem. Radiochem., 19, 185 (1976). 

Table 12.1 shows how electrons are gained and lost when nitrogen, oxygen, fluorine, sodium, magnesium, and aluminum form monatomic ions that are isoelectronic with a neon atom. The pattern built around neon is duplicated for other noble gases. Thus, phosphoms, sulfur, chlorine, potassium, calcium, and scandium (Z = 21) are the elements that form ions that are isoelectronic with argon, and five of the elements on either side of krypton form ions that duplicate the electron configuration of krypton. 

Acidify 0.5 mL of the alkaline solution from the fusion with dilute nitric acid (indicator paper) and, if nitrogen or sulfur has been found present, boil the solution (hood) to expel HCN or HjS. On addition of a few drops of silver nitrate solution, halide ion is precipitated as silver halide. Filter with minimum exposure to light on a 2.5-cm funnel, wash with water, and then with 1 mL of concentrated ammonia solution. If the precipitate is white and readily soluble in ammonium hydroxide solution it is AgCl if it is pale yellow and not readily soluble it is AgBr if it is yellow and insoluble it is Agl. Fluorine is not detected in this test since silver fluoride is soluble in water. 

Much of the chemistry of oxygen can be rationalized in terms of its electronic structure (2s 2p ), high electronegativity (3.5) and small size. Thus, oxygen shows many similarities to nitrogen (p. 412) in its covalent chemistry, and its propensity to form H bonds (p. 52) and double bonds (p. 416), though the anionic chemistry of 0 and OH is much more extensive than for the isoelectronic ions N , NH and NH2. Similarities to fluorine and fluorides are also notable. Comparisons with the chemical properties of sulfur (p. 662) and the heavier chalcogens (p. 754) are deferred to Chapters 15 and 16. 

The striking feature of the isotopic ratios that you should note in this spectrum is the low [M + l ]/[M ] ratio and similar ion-abundance ratios (m/z 72 is not tabulated, since its intensity is <0.2). Because of these ratios the elements carbon, oxygen, silicon, sulfur, and chlorine are all eliminated from consideration. Note that there are intense peaks at [M — 19] and (M — 2 X 19) as well as m/z 19 indicating the presence of fluorine. [Nitrogen trifluoride]... 

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