The New York herald., 1922-07-02

l. With all tho heavy positive cleo
irons and only some Of the negative
electrons constituting this nucleus, II
is evidently positively charged. An A
particle is also positively charged with
a known charge. Prof. Rutherford
suggested that a collision between
them. indicated by sharp bend in
the path of the A particle as It passes
through the air. may be due simply
to the effect of the repulsive force
between these two charges when they
come very near together. Darwin cal
culated on this hypothesis the frac-
ton of all the observed reflections of
A particles shooting through air or
any other substance. which should be
within any specified angular limits.
When this calculation was compared
with the experimental measurements
of reflections through various angles
it was found that there was exact
agreement only provided the force be-
tween the A particle and the nucleus is
taken to vary inversely as the square
of the distance between them. and
provided the charge of the nucleus Of
the atom is taken equal Tin electronic
units) to It's atomic number. The
atomic number Of an element Is its
order In the periodic table. e.,
for hydrogen. for helium, for
lithium, &c.
Some Energy Extracted
~ From X-Ray Beam
This conclusion was verified by an
entirely independent method. When a
beam of X-ray passes through sub
stances some of its energy Is abb
stracted and sent out in all directions.
The amount. character and distribu-
ton OF this scattered radiation have
been exactly accounted for by ascrib-
ing the scattering to the action of the
electrons outside the nuclei of the
atoms. These electrons are acceler-
ated by the electric forces in the X-ray
beam, and as result of their accel-
Grafton give rise to the scattered ra-
diation. Sir j. J. Thomson calculated
the proportion of the energy Of an
X-ray beam scattered by each mega
tive electron in its path. Dividing the
observed amount of scattering by this
gives the number of negative electrons
ldhiiiS part III tHC sSottSliiiS' l%iNio
ing this by the number OF atoms gives
the number of scattering electrons per
atom, which Is found equal to its
atomic number. But the number of
scattering electrons (electrons outside
the nucleus) must obviously equal the
positive charge of the nucleus. in cleo
tronic units, thus verifying the pre-
vious conclusion regarding the nuclear
charges of atoms.
Finally, a relation between the
atomic number of an element and the
vibration frequency OF the radiation
constituting it's X-ray spectrum was
discovered by Moseley. 1t can be ex-
pressed rather accurately by saying
that the square foot of the frequency
of any particular type Of X-radiation
is directly proportional to the atomic
number Of the radiating element. This
has been satisfactorily accounted for
only by supposing that the atomic
number of an element is equal to the
electronic charge on its nucleus, /. e.,
to the excess of positive over negative
electrons In its nucleus.
Atomic Constituents.--Thef foregoing
evidence and much additional evidence
leads to the conclusion that the va
rious chemical elements have atoms
constituted as shown IN the following
taole, which contains only few ex
amples. Those elements bracketed to-
gether are isotopes: