QUESTIONS AND PROBLEMS 135 



244. How would you deduce the valency of elements which do not unite 



with hydrogen? Give examples of univalent, bivalent, and 

 trivalent metals. Name some metals which have more than one 

 valency, as shown by the existence of two series of salts. 



245. Give examples of univalent, bivalent, trivalent, and quadrivalent 



groups of elements or "radicles," and illustrate each by examples. 



246. Write the formulae for calcium nitrate, aluminium phosphate, 



ferrous carbonate, cupric silicate, and ammonium sulphite. 



247. The properties of the elements are said to be dependent upon their 



atomic weights. Illustrate this by the variation in properties 

 between the elements of (i) a group of metals and (2) a group of 

 non-metals. 



248. Tabulate the chlorides, hydroxides, oxides, sulphides, nitrates, 



sulphites, sulphates, carbonates, phosphates, and silicates of 

 hydrogen, ammonium, potassium, sodium, calcium, magnesium, 

 iron (ferrous and ferric), and aluminium, referred to in the fore- 

 going studies. Use the formulae, not the names of the 

 compounds. 

 "249. Determine the relative density of carbon monoxide (H = i), and 

 from this calculate the molecular weight. Does it correspond 

 with the formula CO ? 



