‘
’
”
7-3.
THE SCATTERING oF ALPHA PARTICLES 143
with the nucleus, and also the fractional number of particles that
mightbe expected at the-various angles. Thus,
N 64
,
505654
2
'
N = M—âv4
-
nzZ2 .
__rÿ/
)
(7—8)
\—.»—I
source
foil
observation position
'
'
’
where N is the number of alpha particles each second which reach
one square centimeter of a screen located ? centimeters from the
center of the €foil and at the angle . No is the corresponding
number at Zero angle when the foil has been removed. The charge
of the electron is a while M is the mass and 0 the velocity of the
alpha particle. Z is the number of electron units of charge on the
nucleus, 71 is the number of atoms per
cubic centimeter and -z‘ is the
'
thickness of the foil in centimeters.
_
.
’
This equation has been _subjected to extensive tests4 and
proven
to be correct underthe conditions for which it was derived.
It is, therefore, to be concluded that the basic assumption of a -
nuclear atom, upon which it rests, has also been established.
Let the chemical elements
arranged in sequence, from the
lighteSt, hydrogen, to the heaviest, uranium, and numbered ’
-
1,
3, etc.
These are the atomic numéeïrofthe elements. The
‘
numbers for. the quan—
tity Z of equation. 7—8,,thus ,proving that the, “atomic number is
equal to the {number
on
There
will then
chargeZe,
by Z.
.
negative electrons
_
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