PRINCIPLES OF CHEMISTRY 127 



hydrogen and 16 parts of oxygen, both of which are gases, 

 water, a liquid, is formed. 



131. Elements. Elements cannot be decomposed by 

 any known method or divided into anything simpler. The 

 smallest particles of elements are known as atoms. Elements 

 are sometimes found alone in the earth, as are pure copper 

 and gold, but are usually associated with other elements. 

 Nearly eighty elements have been discovered and named, 

 but many of them are not commonly found. In chemistry, 

 every elementary substance is represented by what is called 

 a symbol, which is usually a single capital letter or one capital 

 letter and one small letter. Symbols are used to save time 

 in writing and to describe briefly and clearly the composition 

 of a complicated compound substance. 



Frequently the symbol for a substance is derived from the 

 first or the first and second letters of the Latin term for the 

 substance. For instance, Cu is the symbol for copper, and 

 the Latin term from which it is derived is cuprum. In like 

 manner, zinc, carbon, manganese, and silver are designated 

 by the symbols, Zn, C, Mn, and Ag. Latin has furnished 

 a number of the symbols for others of the common elements; 

 thus, the symbol for sodium is Na (natrium), for potassium, 

 K (kalium), and for iron, Fe (ferrum). The symbol Hg 

 (hydrargyrum) for mercury is from the Greek. 



132. Metallic and Non-Metallic Elements. The most 

 satisfactory way to classify elements is to consider them 

 as metals or non-metals. Non-metallic elements are those 

 that combine readily with metals to form compounds; for 

 example, chlorine, sulphur, silicon, phosphorus, etc. The 

 non-metallic elements have not so much trade importance 



