Evolution and Devolution of the Elements. 43 
in such a way that the number of electrons transferred is a 
minimum ; so, with sodium and chlorine, the sodium will give 
one electron to the chlorine, and not receive seven from it. 
That this is so, is evident from the following considerations. 
Given that a system of either eight or zero electrons round an 
element is the most stable, an element with seven electrons, 
or with one only, is very near the stable position. In 
the first case, the element with seven electrons will very 
readily acquire another ; and in the second case, the element 
with only one will very readily give it up. So also an element 
with two electrons will readily lose them, but not so readily 
as an element with only one ; three electrons will be lost or 
gained still less readily ; and finally, in the case of an element 
with four electrons, it is a matter of indifference whether 
others are gained or lost. In other words, monovalent 
elements may be said to be, in general, the most electro- 
positive, heptavalent the most electronegative, and tetravalent 
ones to be electrically neutral. 
Loss or gain of electrons, according to the above idea, 
constitutes the principal valency of an element, and it must 
be noted that more than four electrons never leave or approach 
one element, and that, moreover, unless the outer ring is 
highly distorted, there is only one principal valency. 
Now in addition an element may have secondary valencies. 
This idea is due to Abegg, but he assumes that each element 
has one principal and one secondary valency, and that the 
sum of these is eight. Also in the first three groups the 
secondary valency is latent. It seems more reasonable to 
suppose that an element may have more than one secondary 
valency, and apparently these secondary valencies are either 
all even or all odd. If this be so, we may tabulate the 
number of electrons which any given ring will lose or take, 
bearing in mind that there is only one principal valency. Thus : 
A monovalent ring will lose 
A divalent ,, ,, 
A trivalent „ ,, 
A tetravalent ., ,, 
A pentavalent „ ,, 
A hexavalent ,, „ 
A heptavalent „ ,, 
An octovalent ,, ,, 
In this it will be noticed that the tetravalent ring has no 
principal valency, and this would be expected, since it is the 
connecting link between elements with positive and negative 
principal valencies. 
In accordance with the principle of minimum movement of 
electrons, it will be seen that when an element has several 
secondary valencies, i it will for preference exert that which 
1 
electron 
or 
acquire 
1, 
3, 5, or 7. 
2 
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2 
4, or 6. 
3 
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3 
or 5. 
2 or4 
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2 
or 4. 
3 or 5 
M 
,, 
3. 
2, 4, or 6 
)» 
,, 
2, 
1, 3, 5, or 7 
,, 
,, 
1. 

,, 
,, 
0. 
