Group VII

The most important trend to be noted in the covalent hydrides is the change in acid-base behaviour as we cross a period from Group IV to Group VII. In Period 1, we have... 

GROUP VII THE HALOGENS 325 OTHER DISPLACEMENT AND OXIDATION REACTIONS... 

The following table shows the atomic numbers of the elements in Group VII of the Period Table and the melting points of their hydrides. 

Group VII. Compounds that contain N or S which are not in Groups I-IV. Many of the compounds in this group are soluble in concentrated sulphuric acid. 

Group IV. The student should remember that the hydrochlorides of some bases are sparingly soluble in cold water and should therefore not be misled by an apparent insolubility of a compound (containing N) in dilute hydrochloric acid. The suspension in dilute hydrochloric acid should always be filtered and the filtrate made alkaline. A precipitate will indicate that the compound should be placed in Group IV if no precipitate is formed, the compound is relegated to Group VII. 

Group VII. This group comprises all compounds containing N or S which are insoluble in water and are indifferent (i.e., insoluble in dilute acid or alkali). 

The imides, primaiy and secondary nitro compounds, oximes and sulphon amides of Solubility Group III are weakly acidic nitrogen compounds they cannot be titrated satisfactorily with a standard alkaU nor do they exhibit the reactions characteristic of phenols. The neutral nitrogen compounds of Solubility Group VII include tertiary nitro compounds amides (simple and substituted) derivatives of aldehydes and ketones (hydrazones, semlcarb-azones, ete.) nitriles nitroso, azo, hydrazo and other Intermediate reduction products of aromatic nitro compounds. All the above nitrogen compounds, and also the sulphonamides of Solubility Group VII, respond, with few exceptions, to the same classification reactions (reduction and hydrolysis) and hence will be considered together. 

Volatile hydrides, except those of Periodic Group VII and of oxygen and nitrogen, are named by citing the root name of the element (penultimate consonant and Latin affixes. Sec. 3.1.2.2) followed by the suffix -ane. Exceptions are water, ammonia, hydrazine, phosphine, arsine, stibine, and bismuthine. 

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