The Halogens Except Fluorine

To the resulting cooled solution, add 2 drops (Pasteur pipet) of aqueous 0.1 M AgNOs solution. 

A heavy curdy-type precipitate is a positive test for the presence of Q, Br , or 1 ion. A faint turbidity is a negative test. 

AgF is not detected by this test since it is relatively soluble in water. 

The silver halides have different solubilities in dilute ammonium hydroxide solution. 

Centrifuge the test tube and contents and remove the supernatant liquid using a Pasteur filter pipet. Add 0.5 mL (calibrated Pasteur pipet) of dilute ammonium hydroxide solution to the precipitate and stir with a glass rod to determine whether the solid is soluble. 

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The halogens, except fluorine, can be oxidized to positive oxidation states. Most commonly you will encounter these positive oxidation states in a set of compounds called halogen oxyacids and their ions. 

The halogens (except fluorine) exhibit both electron-accepting and electron-re-leasing behaviors. Since they resemble the noble gas elements only in regard to electron releasing, this aspect of the chemistry of the two families will be discussed first. The more familiar acceptance of electrons by halogens is discussed later in the chapter. 

All of the halogens except fluorine, which is more electronegative than oxygen, form oxyanions in which the valence of the halogen varies, e.g., chlorite, chlorate, perchlorate. 

For laboratory preparations of small quantities of the halogens (except fluorine), oxidation of acidic solutions containing the appropriate halide, using permanganate or manganese dioxide, is convenient. 

Atoms of higher atomic number can expand the valence shell to more than eight electrons. These atoms include sulfur, phosphorus, and the halogens (except fluorine). 

Chlorous acid, HCIO2, is the only known halous acid. All the halogens except fluorine form halic and perhalic acids. The Lewis structures of the chlorine oxoacids are... 

All the halogens except fluorine form Xa cations in the solid state, whereas in solution only Bra ai d I3 have been identified. The I5 cation has been isolated in the solid and observed in solutions. The existence of I7 cation was derived only from a thermal study. Preparations of the compounds and their properties are summarized in Table 1. 

The HOI (hypoiodous acid) thus produced could then be scavenged by a second iodide ion to produce molecular iodine this is a well-known reaction for all the halogens, except fluorine ... 

The halogens are all one electron short of a noble gas electron configuration. They are the most electronegative elements in their respective periods and are therefore very reactive. They do not naturally occur in their elemental form. The source of most of the halogens (except fluorine) is the dissolved salts present in seawater. The major sources for fluorine are several different minerals, including fluorspar (Cap2) and fluoroapatite [CaioF2(P04)6l. 

All the halogens except fluorine combine with various numbers of oxygen atoms to form a series of oxyacids, as shown in Table 20.10. The strengths of these acids vary in direct proportion to the number of oxygen atoms attached to the halogen, as we discussed in Section 14.9. 

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