50 THE THEORY OF IONS 



B. Anions. 



1. MONADS : OH, F, Cl, Br, I, N0 3 , C10 3 , 



C 2 H 3 2 and the anions or 

 radicals of all monobasic acids. 



2. DYADS : S0 4 , S0 3 , S 2 3 , C0 3 , S (sulphide), 



C 2 4 , and all anions of dibasic 

 acids. 



3. TRIADS : P0 4 , and anions of all tribasic acids. 



The amount of the electrical charge carried by 

 the ions varies with the valency of the element or 

 elements, as before stated. Thus, 1 gramme- 

 molecule of H ions carries a charge of positive 

 electricity estimated as 96,550 coulombs. This is 

 the standard of the capacity of ions for carrying 

 electricity. All monovalent ions or monads carries 

 the same in proportion to their atomic weight. 

 Divalent ions or dyads carry twice as much, there- 

 fore a gramme-molecule of calcium ions carry 

 2 x 96,550 coulombs of positive electricity, and each 

 ion would require two ions of negatively charged 

 chlorine to satisfy its valency. Similarly, the 

 trivalent nitrogen ion would require three ions of 

 hydrogen to satisfy its valency or neutralise its 

 electricity ; and a gramme-molecule of N ions would 

 carry 3 x 96,550 coulombs. 



It is to be observed that the valency of some ions 

 may be changed. Carbon may be either dyad or 

 tetrad ; sulphur, a dyad, tetrad, or hexad ; nitrogen, 

 a triad' or pentad ; phosphorus, a triad or pentad ; 

 and chlorine may be monad, triad, pentad, or hep tad. 

 This changeable character is, however, only shown 

 towards btrdfes jbh&t ^,re -more eJectm-nega^ive than 



