Balancing Nuclear Reactions
In nuclear equations, with the reactants
(starting materials – on the left side of an
equation) and products (final products – on the
right side of an equation)
Atomic numbers must equal on the left and right
sides
and
Mass numbers must equal on the left and right
sides
Use a particle or isotope to fill in the missing
protons and neutrons
Nuclear Reactions
• Alpha emission
Note that mass number (A) goes down
by 4 and atomic number (Z) goes down
by 2.
Nuclear Reactions
• For example, if Uranium-238 undergoes
alpha decay
Alpha Particle
Mass Number
238
92
U
4
2
He
Atomic Number
Th
234
90
Final Element
Note How Top and Bottom
Number’s Add Up on Each
Side!
Nuclear Reactions
• What if Radon-222 undergoes alpha
decay?
Alpha Particle
Mass Number
222
86
Rn
4
2
He
Atomic Number
Po
218
84
Final Element
Note How Top and Bottom
Number’s Add Up on Each
Side!
Nuclear Reactions
• What would be the balanced nuclear
equation if Plutonium-244 goes through
alpha decay?
Mass Number
244
94
Pu
Alpha Particle
4
2
He
Atomic Number
U
240
92
Final Element
Note How Top and Bottom
Number’s Add Up on Each
Side!
Nuclear Reactions
• Beta emission
Note that mass number (A) is
unchanged and atomic number (Z)
goes up by 1.
Nuclear Reactions
• For example, if Uranium-238 undergoes
beta decay
Beta Particle
Mass Number
238
92
U
0
-1
e
Atomic Number
Np
238
93
Final Element
Note How Top and Bottom
Number’s Add Up on Each
Side!
Nuclear Reactions
• What if Neptunium-237 undergoes beta
decay?
Beta Particle
Mass Number
237
93
Np
0
-1
e
Atomic Number
Pu
237
94
Final Element
Note How Top and Bottom
Number’s Add Up on Each
Side!
Nuclear Reactions
• What if Curium-249 undergoes beta
decay?
Beta Particle
Mass Number
249
96
Cm
0
-1
e
Atomic Number
Bk
249
97
Final Element
Note How Top and Bottom
Number’s Add Up on Each
Side!
Nuclear Reactions
• Gamma Ray Emission
Nothing changes!
Decay Chains
• For example, if Uranium-238 undergoes
alpha decay and then beta decay…
238
92
U
4
2
He
Th
234
90
Transition Element
234
90
Th
0
-1
e
234
91
Pa
Decay Chains
Uranium-238 undergoes alpha, beta, and alpha
decays in that order
238
92
U
4
2
He
Th
234
90
Transition Element
234
90
Th
0
-1
e
234
91
Pa
Transition Element
234
91
Pa
4
2
He
Ac
230
89