6 
The Philippine Journal of Science 
1921 
other hand, the maximum negative valence represents the number of 
electrons which the atom must take up to reach a stable form like that of the 
inert gases. 
Langmuir further brings out the facts, at least by inference, 
that the actual negative valence in any compound, if exhibited at 
all, is almost always the same as the maximum, but the actual 
positive valence is often less than the maximum, giving two or 
more classes of compounds of the same metal, such as the cu- 
prous and cupric compounds. 
It seems important to the writer to express graphically, when 
writing structural formulas, the actual positive or negative va- 
lence exhibited by each atom. 
PROPOSED SYSTEM FOR WRITING STRUCTURAL FORMULAS 
1. Valence . — Represent th^' maximum electronegative valence 
of an atom in the ordinary way: 
I | 
H — , F — , -0— , — N— , — C — , B— . 
I I / \ 
Each line represents the organic chemist’s “unsatisfied bond,” 
the physical interpretation of which is vacancy for one more 
electron in the shell. The nitrogen atom, for example, needs 
three electrons to complete a shell of eight. The number of 
“unsatisfied bonds” for each electronegative atom can readily 
be found by consulting Table 1. Electropositive valence is on 
no account to be represented by “unsatisfied bonds” as it never 
causes direct union between atoms. It may be represented as 
follows : 
Na 1 , Ca 11 , A1 IH . 
2. The salt-forming union . — It is evident that an atom may fill 
a vacancy in its shell (satisfy a bond) by simply acquiring an 
electron, thus becoming a negative ion. 11 It may even create 
more bonds by the reverse process : F — becomes F ~ — 0 — be- 
+ ' I + 
comes 0 , H — becomes — H — , — N — becomes — N — . 
I I 
Negative ions having no unsatisfied bonds form stable saltlike 
compounds with metallic ions: 
Na + CF, Ca++ :::::: 0 
It is to be noted that while the formation of ions is due to the 
shell-completing forces of one of the atoms involved, the union 
11 For the lack of a better wPrd, this term seems to be quite generally used 
for a charged atom even though it may not be mobile. 
