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SMITHS INTERMEDIATE CHEMISTRY 



The valence of the atomic weight of manganese changes in the 

 course of this action from 4 to 2. When MnO acts on HC1, 

 however, manganese is bivalent throughout. 



Exceptional Compounds. A few compounds will be met 

 with in which an element shows an exceptional valence. Thus, 

 nitrogen gives two series of compounds of N m and N v . Bui 

 there are three oxides, N 2 O, NO, and NO 2 , in which the valence of 

 nitrogen seems to be one, two, and four, respectively. However, 

 these are single compounds, not belonging to any series, and are the 

 only compounds of nitrogen showing any of those three valences. 



Again, FeO and Fe 2 O 3 belong to the two regular series of com- 

 pounds of iron. But there is the magnetic oxide, Fe 3 4 , where 

 the valence of iron appears not to be a whole number, but 8/3 or 

 2|. In this case the chemist makes the valence regular by sup- 

 posing the magnetic oxide to be a compound of the other two 

 oxides, and writing its formula, FeO,Fe 2 3 . 



A List of Valences and Charges. The following table 

 contains the valences of some familiar ions and the commonest 



