Chapter 22 – Nuclear Chemistry
Nuclear Symbols
Mass number
(p+ + no)
235
92
U
Atomic number
(number of p+)
Element symbol
Types of Radioactive Decay
alpha production (a): helium nucleus
238
4
234
92 U  2 He  90Th
0
beta production (b):  1 e
234
234
90Th  91Pa

0
1e
4
2+
He
2
Alpha
Radiation
Limited to
VERY large
nucleii.
Beta
Radiation
Converts a
neutron into
a proton.
Types of Radioactive Decay
gamma ray production (g):
238
4
U

92
2 He

234
90Th
 2 00 g
0
positron production 1 e :
22
0
Na

11
1e

22
10 Ne
electron capture: (inner-orbital electron
is captured by the nucleus)
201
0
201
Hg

e

80
1
79 Au
 00 g
Types of Radiation
Deflection of Decay Particles
attract
Opposite charges_________
each other.
repel
Like charges_________
each other.
Nuclear
Stability
Decay will occur in
such a way as to
return a nucleus to
the band (line) of
stability.
Half-life Concept
Sample Half-Lives
A radioactive nucleus reaches a stable state
by a series of steps
A
Decay
Series
Nuclear Fission and Fusion
•Fusion: Combining two light nuclei to form
a heavier, more stable nucleus.
3
1
4
0
2 He  1H  2 He  1e
•Fission: Splitting a heavy nucleus into two
nuclei with smaller mass numbers.
1
235
142
91
1
0 n  92 U  56 Ba  36 Kr  30 n
Fusion
Energy and Mass
Nuclear changes occur with small but measurable
losses of mass. The lost mass is called the mass
defect, and is converted to energy according to
Einstein’s equation:
DE = Dmc2
Dm = mass defect
DE = change in energy
c = speed of light
Because c2 is so large, even small amounts of
mass are converted to enormous amount of
energy.
Fission
Fission Processes
A self-sustaining fission process is called
a chain reaction.
Neutrons
Causing
Event
Fission
subcritical
<1
critical
=1
supercritical
>1
Result
reaction stops
sustained reaction
violent explosion
A Fission Reactor
Chernobyl
• Nuclear powerplant
meltdown 1986