8
1.
THE CHARGE OF THE ELECTRON
F araday’s second law states that if the same quantity
of electricity is passed through different solutions, the
masses liberated
are
directly proportional
to
the atomic we1ghts and 1nversely
proportional
to
the valences
of the
elements dep031ted.*
example, if 9649 electromagnetic units of quantity of electr1crty
are passed through water which contains a small amount of ac1d,
8.000 grams
of oxygen (atomic weight = 16.000, valence = 2)
and 1.008
of hydrogen (atomic weight = 1.008, valence = 1)
will be given
at the positive and negative electrodes respectively. In 1874, Stoney advanced the viewpoint that, since this
law is true and since the elements are known to be made up of ‘
_
atoms, then electricity must also be granular.
The quantity of electricity needed to deposit a mass, in grams,
equal to the atomic weight divided by the valence (one gram_
equivalent) is a universal constant called thefamdcz_y, (F).
'
F = 9649 e.m.u./gram equivalent.
=
2893 X 1014 e.s.u./gram equivalent.
From the suggestion of Stoney and for univalent elements,
this quantity of electricity may be divided into a large number (N)
'
‘
of
charges (6), each of which is associated with one atom.
N is known as Avogadro’s number. If the element has a valence
_
v, thecharge
each atom will
and thehumber of atoms
deposited by each faraday will be N / 2). Then
.
,»
F =
%Î —- ev,
.
(1—15)
or. .
-
,
_
.
F = Ne.
(l'—16)
the produCt Ne for gaseous ions have been
made fr0m
“relation between this quantity and the
measurablemob1htles and
ions.
The values
With —
themeasurements1nelectroly31s
not,
so