242
11.
SPONTANEOUS DISINTEGRATION
one
radon will produce a saturation current of 0.92
amperes.
Hence, one Mache unit is the equivalent of3.64 X 10—10
_
cùries per liter.
-
In order to determine the activity of a given substance it is
only necessary
to compare the rates of fall of the leaf of an electroscope
in which the unknown and a standard have been placed in
succession.‘
Certain
necessary
precautions are discussed in
chapter 17.
-
—
11—4.
Radioactive
Series.—Rutherford
and
Soddy have
shown that when a radiactive substance, the parènt, emits an alpha
or a beta ray, an entirely new substance, the product, is left which
-
240
Uranium-Radium Series
Actînium Series
Thorium Series
234
‘
Ë0226--'y/
o..æ
%
_
-
": 216—
“___
-==…—_
214 .“
-—°-_
,
-
--m
“‘
…-=-, , %
AcB .__
_,
.
==--aær1.u…@
â8î------I@I--i J--L
_
F1G. 11—2.
The radioactive series.
has different chemical and physical properties from the parent.
Thus, radioactivity is a nuclear phenomenon.
Starting with uranium and thorium, the radioactive substances
change from one material into another, branch along three distinct
paths and end in three isotopic forms of lead, as given in table
16 at the end of the book and as shown in gure 11—2. Potassium
(K“), rubidium and samarium are also radioactive, but only to
_
an exceedirig small degree.
'
The rate at which these transformations take place is diHerent
f for each substance in the series.
Some radioactive substances
_
,
have'a life of many hundreds of years, as represented by the large
»
”circles of gure 11—2, While others last only a fraction of a second.
In other words, the probability that the nuclei of certain atoms
11.
SPONTANEOUS DISINTEGRATION
one
radon will produce a saturation current of 0.92
amperes.
Hence, one Mache unit is the equivalent of3.64 X 10—10
_
cùries per liter.
-
In order to determine the activity of a given substance it is
only necessary
to compare the rates of fall of the leaf of an electroscope
in which the unknown and a standard have been placed in
succession.‘
Certain
necessary
precautions are discussed in
chapter 17.
-
—
11—4.
Radioactive
Series.—Rutherford
and
Soddy have
shown that when a radiactive substance, the parènt, emits an alpha
or a beta ray, an entirely new substance, the product, is left which
-
240
Uranium-Radium Series
Actînium Series
Thorium Series
234
‘
Ë0226--'y/
o..æ
%
_
-
": 216—
“___
-==…—_
214 .“
-—°-_
,
-
--m
“‘
…-=-, , %
AcB .__
_,
.
==--aær1.u…@
â8î------I@I--i J--L
_
F1G. 11—2.
The radioactive series.
has different chemical and physical properties from the parent.
Thus, radioactivity is a nuclear phenomenon.
Starting with uranium and thorium, the radioactive substances
change from one material into another, branch along three distinct
paths and end in three isotopic forms of lead, as given in table
16 at the end of the book and as shown in gure 11—2. Potassium
(K“), rubidium and samarium are also radioactive, but only to
_
an exceedirig small degree.
'
The rate at which these transformations take place is diHerent
f for each substance in the series.
Some radioactive substances
_
,
have'a life of many hundreds of years, as represented by the large
»
”circles of gure 11—2, While others last only a fraction of a second.
In other words, the probability that the nuclei of certain atoms