2 | ‘The Philippine Journal of Science 1921 
results of a reaction which has never been performed. The 
method used by Langmuir in applying the theory, however, ap- 
pears to the writer to be somewhat cumbersome for general use, 
and to obscure, by its indirectness, some of the value of the 
theory. The purpose of the present article is to present a sys- 
tem for writing structural formulas which will be as simple 
and direct as possible, and at the same time represent the mole- 
cules as accurately as possible in terms of modern atomic theory. 
It is hoped not only to furnish by this means a simple method 
for practical application of the theory in its present stage of 
advancement but: even to develop certain valence relationships 
which have not hitherto been clearly expressed. 
While it is assumed that anyone interested in the subject 
is already familiar with recent developments of the octet theory 
in the hands of Langmuir and others, for the sake of clarity the 
subject will be briefly reviewed. 
THE STRUCTURE OF ATOMS 
NUCLEUS ‘ 
In the light of recent physical evidence the essential portion 
of any atom is a minute nucleus composed of positive units of 
‘electricity (sometimes called positive electrons) and a smaller 
number of negative units (sometimes called negative electrons, 
but usually simply electrons) very closely packed together and 
bound by the most powerful forces known. The positive units 
are all identical, each having a mass of approximately 1, ex- 
pressed in atomic weight units. Similarly the (negative) elec- 
trons are all identical, but have negligible mass. Each electron 
in the nucleus neutralizes one positive unit, so the total outside 
electrical effect, called the nuclear charge, is measured by the 
number of positive units less the number of electrons (negative 
units). This difference is called the atomic number of the nu- 
cleus. 
NEUTRAL ATOM 
Except under very unusual circumstances, such as when trav- 
eling with extreme velocity, a nucleus is never found alone, be- 
cause it normally attracts as many electrons as its atomic num- 
ber, forming an electrically neutral atom. These electrons do not 
enter the nucleus but arrange themselves in nearly spherical 
concentric shells, which vary in number from one to seven ac- 
‘Harkins, W. D., Journ. Am. Chem. Soc. 42 (1920) 1956; Rutherford, 
E. E., Proc. Roy. Soc. London 97A (1920) 374-401. 
