204 CHEMISTRY. 



281. Classification of Metals. Metals may bo divided 

 for the sake of convenience into nine groups, according 

 to their attraction for oxygen and their chemical relations 

 generally : 



GROUP I. The Metals of the Alkalies: Potassium, Sodium [and the 

 very rare metals Lithium, Caesium, and Rubidium]. 



GKOUP II. Metals of the Alkaline Earths: Barium, Strontium, and Cal- 

 cium. 



GROUP III. Metals of the Earths : Aluminium [and the very rare met- 

 als Glucinum, Yttrium, Erbium, Cerium, Lanthanium, 

 Didymium]. 



GROUP IV. Magnesian Metals. Magnesium, Zinc [Cadmium, and In- 

 dium]. 



GROUP V. Iron Group. Manganese, Iron, Cobalt, Nickel, Chromium 

 [and Uranium]. 



GROUP VI. Tin Group. Tin [and the exceedingly rare metals Titanium, 

 Zirconium, Thorinum, Columbium, Tantalum, Molyb- 

 denum, and Tungsten]. 



GROUP VII. Arsenic Group. Arsenic, Antimony, Bismuth [and Vana- 

 dium]. 



GROUP VIII. Three Metals not closely related. Copper, Lead [and 

 Thallium]. 



GROUP IX. Noble Metals. Mercury, Silver, Gold, Platinum [and the 

 accompanying metals Palladium, Rhodium, Ruthenium, 

 Iridium, and Osmium]. 



Of these forty-nine elementary substances we shall study 

 only twenty-three, the remainder (inclosed in brackets in 

 the above paragraphs) are far too rare and of too little im- 

 portance and interest to engage our attention. Sometimes 

 arsenic and antimony are placed for chemical reasons among 

 the non-metallic bodies alongside of phosphorus, but this is 

 only a matter of taste. The line drawn between the non- 

 metals and the metals is not absolute, but merely a con- 

 venient way of distinguishing them. 



There is another way of grouping metals often followed, viz., with refer- 

 ence to their atomicity ; but this separates metals which seem to belong nat- 



