NSCI 1322 Lecture Notes - Lecture 9: Carl Wilhelm Scheele, Chalcogen, Liquid Oxygen
12 Jan 2017
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Document Summary
Group 6a, like the preceding groups, shows the trend from nonmetallic to metallic as you proceed from top to bottom of the column of elements. Although the chemical properties of selenium and tellurium are predominantly those of nonmetals, they do have semiconducting allotropes as expected of metalloids. Oxygen, a second-period element, has rather different properties from those of the other members of group 6a. Oxygen combines with almost every element only some of the noble gases have no known oxygen compounds. The chemistry of oxygen is therefore very important, though we frequently discuss it in the context of other elements. In fact, much of the chemistry of the elements discussed concerns either their reactions with oxygen or the properties of their oxides and oxoacids. Oxygen is produced in enormous quantity from air. As described in the discussion of nitrogen, air is first liquefied, then distilled.
