'
7—2.
THE NUCLEAR ATOM
141
distance or mean—free—path of the air molecules between their
mutual collisions (about 10“5 centimeters) and concluded that the
atoms were not solid spheres.
Since atoms cannot be considered as solid spheres, we proceed
to a discussion of their inner structure.
:
_
7—2.
The Nuclear AtÔm.—The experiments in which the
charge—to—mass ratio of electrons was measured (Chapter 2) indi—
cated that negative electricity exists inside the atoms. _If the atom
contains negative electricity alone it would tend to y apart under
the forces of repulsion between like charges. 'Thus, the presence
of a restraining positive charge is
Many attempts were
made in the past to seCure a satisfactory geometrical distribution
of these positive and negative charges such that a stable atom
would result and various known properties of the atom would be
explained. Obviously, thetotal negative charge had to be equal
to the total positive charge if the atoms were to be electrically
neutral.
'
-
=
"
…
'
In 1911, Rutherford proposed his nuclear
This consisted
.,
of a heavy, positivelycharged nucleus, Surrounded by negative
'
electrons in such numbehas to make.the total charge equal to zero.
_
He and his colleaigues tested this modelby studies of
the scattering
of alpha particles[from thin,foils,' as discussed »inÏthe nextsection.
_In 1913, Niels' Bohr used this model successfully to predict the
'
frequencies of the
from
atomsänd in 1914,
Moseley used
«mo,del _thdeduce the
.
emitted-by d1'erentelemths
*
,—
'
_
» ‘fAs;we shallsee 1nth1s
the
.
three
requ1rementsofanat0mm0delnamely
;> >
.
-
-
_
.
2Anmtermed1atesectwnassocmtedw1‘chxrays
-‘
3Anuclearreglonwhichdetermmesthekmdof element &?
‘
.
?handandlsassoaaædwhnatumlandafüclalrëdiëä >>
‘,
1ntegrat10ns
: i — ”-
7—2.
THE NUCLEAR ATOM
141
distance or mean—free—path of the air molecules between their
mutual collisions (about 10“5 centimeters) and concluded that the
atoms were not solid spheres.
Since atoms cannot be considered as solid spheres, we proceed
to a discussion of their inner structure.
:
_
7—2.
The Nuclear AtÔm.—The experiments in which the
charge—to—mass ratio of electrons was measured (Chapter 2) indi—
cated that negative electricity exists inside the atoms. _If the atom
contains negative electricity alone it would tend to y apart under
the forces of repulsion between like charges. 'Thus, the presence
of a restraining positive charge is
Many attempts were
made in the past to seCure a satisfactory geometrical distribution
of these positive and negative charges such that a stable atom
would result and various known properties of the atom would be
explained. Obviously, thetotal negative charge had to be equal
to the total positive charge if the atoms were to be electrically
neutral.
'
-
=
"
…
'
In 1911, Rutherford proposed his nuclear
This consisted
.,
of a heavy, positivelycharged nucleus, Surrounded by negative
'
electrons in such numbehas to make.the total charge equal to zero.
_
He and his colleaigues tested this modelby studies of
the scattering
of alpha particles[from thin,foils,' as discussed »inÏthe nextsection.
_In 1913, Niels' Bohr used this model successfully to predict the
'
frequencies of the
from
atomsänd in 1914,
Moseley used
«mo,del _thdeduce the
.
emitted-by d1'erentelemths
*
,—
'
_
» ‘fAs;we shallsee 1nth1s
the
.
three
requ1rementsofanat0mm0delnamely
;> >
.
-
-
_
.
2Anmtermed1atesectwnassocmtedw1‘chxrays
-‘
3Anuclearreglonwhichdetermmesthekmdof element &?
‘
.
?handandlsassoaaædwhnatumlandafüclalrëdiëä >>
‘,
1ntegrat10ns
: i — ”-