Chemical Classification 307 



210. It is usual to divide the elements into metallic 

 and non-metallic sections. To the former belong the 

 majority of the elements, all the common metals being 

 included in this class. The distinction between a metal 

 and a non-metal is not a hard and fast one. In general, 

 a metal possesses the following properties, although 

 every metal does not of necessity exhibit all of them. 



(1) Metals are usually of high density. 



(2) They possess a characteristic lustre, and 

 their surfaces may be made to take a high polish. 



(3) They are ductile, i.e. may be readily drawn 

 into wire. 



(4) They are malleable, i.e. may be hammered 

 out into thin sheets without fracture. 



(5) They are good conductors of heat and of 

 electricity. 



(6) They usually exist at ordinary temperatures 

 in the solid state. 



(7) They form oxides which are generally in- 

 soluble in water. Those which dissolve produce 

 alkaline solutions. 



Exercise for Student. 



Classify the metals already mentioned in the text according 

 as they exhibit or otherwise each of the characteristics given above, 

 as far as your knowledge of the properties of each permits. 



To the class of non-metals belong the gases, oxygen, 

 nitrogen and hydrogen already studied, together with 

 the following : carbon, sulphur, chlorine, bromine, 

 iodine, silicon, boron, phosphorus and argon. A few 

 other elements of less common occurrence also belong 

 to the non-metallic group. 



202 



