NUCLEAR CHEMISTRY: INTRO
1. Kinetic Stability : probability that an unstable nucleus will decompose
into more stable species through radioactive decay.
2. All nuclides with 84 or more protons are unstable and will decay.
• Light nuclides where Z = A-Z (neutron/proton ratio is 1).
• Nuclides with even numbers of neutrons and protons are unusually
stable.
• Especially stable nuclides exhibit magic numbers,
2,8,20,28,50,82,126 of neutrons or protons.
• A nuclide is a unique atom of the type.
A
X
•
Z
Alpha decay, emits a
4
2
He
NUCLEAR CHEMISTRY: STABILITY GRAPH
#n
120
110
100
90
80
70
60
50
40
30
20
10
20 p
40 p
60 p
80 p
100 p
NUCLEAR CHEMISTRY: BETA DECAY
14
6
1.
2.
3.
4.
5.
C

14
N
7
0
+
e
BETA PARTICLE
-1
BETA DECAY
THE ATOMIC NUMBER OF THE PRODUCT INCREASES.
NUCLIDES ABOVE THE PENNINSULA (ZONE) OF STABILITY DECAY
WITH BETA DECAY(SEE GRAPH ON OTHER SLIDE).
PENETRATING RADIATION.
THE BETA PARTICLE CONES FROM THE DECOMPOSITION OF A
NEUTRON TO A PROTON AND BETA PARTICLE. THE BETA PARTICLE
IS AN ELECTRON “BORN” IN THE NUCLEUS.
BETA DECAY IS SPONTANEOUS, NOTICE ONLY ONE REACTANT.
1
n
0
1

p
1
0
+
-1
e
NUCLEAR CHEMISTRY: ALPHA DECAY
238
U
92
4

He
2
234
+
Th
90
ALPHA PARTICLE
1.
2.
3.
4.
5.
6.
7.
ALPHA DECAY
THE ATOMIC NUMBER OF THE PRODUCT DECREASES BY 2.
THE MASS NUMBER OF THE PRODUCT DECREASES BY 4.
ALPHA RADIATION IS NON PENETRATING TO HUMAN SKIN,
HOWEVER IT CAN BE INGESTED.
COMMON MODE OF DECAY FOR HEAVY RADIOACTIVE NUCLIDES.
NEUTRON/PROTON RATIO INCREASES.
THE ALPHA PARTICLES ARE POSITIVE, THESE HIGH ENERGY He
ATOMS HAVE LOST THE ELECTRONS, ARE REPELLED BY POSITIVE
ELECTRODES AND ARE AFFECTED BY MAGNETIC FIELDS.
ALPHA DECAY IS SPONTANEOUS.
NUCLEAR CHEMISTRY: POSITRON EMISSION
22
11
Na
0

e
+1
22
+
Ne
10
POSITRON
1.
2.
3.
4.
POSITRON EMISSION
DECAY MODE FOR NUCLIDES BELOW ZONE OF STABILITY.
CHANGES A PROTON TO A NEUTRON.
PRODUCT HAS A HIGHER NEUTRON TO PROTON RATIO.
THE POSITRON IS THE ANTIPARTICLE TO AN ELECTRON THE
REACTION OF A POSITRON WITH A BETA PARTICLE PRODUCES
GAMMA RADIATION .
0
e
+1
0
+
e
-1

0
GAMMA
0
NUCLEAR CHEMISTRY: ELECTRON CAPTURE
201
80
Hg
0
+
e
-1
201

Au
79
+
0 GAMMA
0
INNER ORBITAL SHELL
ELECTRON
ELECTRON CAPTURE
1. AN INNER SHELL ELECTRON IS CAPTURED BY THE NUCLEUS.
FISSION
FISSION IS WHERE A
LARGE NUCLEOUS IS
BOMBARDED BY A SMALL
PARTICLE AND THE
LARGER NUCLEUS
BREAKES DOWN INTO
MORE STABLE SMALLER
NUCLEII. HERE THE
UNSTABLE LARGE
NUCLEUS IS URANIUM-235
AND THE BOMBARDMENT
PARTICLE IS A NEUTRON.
ENOURMOUS
QUANTITIES OF
ENERGY IS
RELEASED
NOTICE YOU GET
MORE
BOMBARDMENT
NEUTRONS THAN
YOU PUT IN