250 



METALS AND THEIR COMBINATIONS. 



Davy discovered methods for the 

 separation of these metals from 

 their oxides. 



Valence of metals. 1 



Univalent. 



Lithium, 



Potassium, 



Sodium, 



Silver. 



Bivalent. 



Barium, 



Calcium, 



Strontium, 



Magnesium, 



Cadmium, 



Zinc, 



Copper, 



Mercury. 



Trivalent. 

 Aluminum, 



Bi, tri, or sexivalent. 

 Chromium, 

 Cobalt, 

 Iron, 



Manganese, 

 Nickel, 

 Molybdenum. 



Bi- and quadrivalent. 

 Iridium, 

 Platinum, 

 Tin. 



Tri- and quinquivalent. 



Antimony, 



Arsenic, 

 , Bismuth. 



Uni- or trivalent. 

 Gold. 



Occurrence in nature. 



a. In a free or combined state. 



Almost exclusively in the metallic state. 



Gold, 



Iridium, 



Platinum, 



Silver, 



Mercury, 



Bismuth, generally metallic, also as oxide and sulphide. 



Copper, rarely metallic ; chiefly as sulphide, oxide, and carbonate 



I As metals or sulphides. 



Potassium, 



Sodium, 



Lithium, 



6. In combination only. 

 Chiefly as chlorides or silicates. 



1 The valence here given is the one chiefly exerted by the elements, but several compounds 

 are known in which some of the metals exhibit a yet different valence ; thus copper and mer- 

 cury seem to be univalent in certain compounds, while some metals exhibiting a valence of 

 six (iron, chromium, etc.) are also bi- and trivalent. 



