Balancing Nuclear Equations
Name: _______________________________________ Period: ______________________
There are two types of nuclear reactions: Fission, where a nucleus breaks into two or more pieces, and
fusion where two or more nuclei combine to form a new element. In nuclear reactions, only the nucleus is
involved. Electrons are ignored. Some atomic nuclei are inherently unstable and spontaneously change or
“decay”. There are four types of decay:
Type
Symbol
Alpha

Beta
e- emission electron
Beta+

e- capture Positron

Gamma
Effect on
Atomic #
decrease by 2
Effect on Atomic
Mass
decrease by 4
increase by 1
0
Stopped by
paper
Aluminum Foil
0
decrease by 1
0
Aluminum Foil
none
none
none
Charge
of Mass(AMU)
particle
+2 (He
4
nucleus)
-1
0
+1
none
Strength
Lead
The net result of , - or + decay is a new element. In b- decay, a neutron decays into a p+ and an ewhich is then ejected. In + decay a p+ captures an e- and transforms into a neutron. But despite the nature
of the reaction the law of conservation of matter still applies and the equations are balanced the same way.
Note particle is a helium nucleus!
Another type of reaction occurs when something impacts a nucleus. These reactions result either in
the nucleus splitting (fission) or the combination of two or more nuclei to form a third, different nucleus
(fusion).
Balancing Nuclear Equations:
Matter must be conserved including all p+ & nû. Example:
219
Decay reaction (decay)
Rn2 4He+ 84
215
n+ 92U
186
Fission Reaction
235
36
92
Po
Kr+
0
Fusion Reaction:
35Cl+1 1H18 36Ar
56
Ba +30
141
1n
another example 2H+1 3H2 4He
17
Practice
Fill in the missing symbol and name the reaction:
1.
2.
3.
H 
U   228
90
Th +
92
144Ce59
144 Pr+
58
Zn 
65
4.
30
__________ ++1 0e
K18 40Ar +
40
5.

3
1
232
19
1
+ n
Be4 7Be +
4 1n+
7
6.
92
235U
   5 5
Cs+3792Rb +
141
7.
0
R n  _______ +24He
129 I 54
222
8.
86
129
53
9.
239
Xe +
Pu  +24He
94
10.
11
'5 O 7 '5 N
8
+
12. Write a balanced nuclear equation for each decay process indicated.
a. The isotope Th-234 decays by an alpha emission.
b. The isotope Fe-59 decays by a beta emission.
c. The isotope Tc-99 decays by a gamma emission.
d. The isotope C-11 decays by a electron capture.
Balance these equations: Note 42He is the only stable isotope of helium.
13. 1H+3 7Li  14.
1
15.
7
Be + n H +________ He
4
What is the balanced nuclear equation for the reaction of curium-246 with carbon-12 to produce
nobelium-254 and four neutrons?
16.
What is the balanced nuclear equation for the reaction of californium-250 with boron-10 to produce
lawrencium-258 and two neutrons?
3
.
1

- decay
1
H2 3He+1 0e
U90
Th+2 4He
232
 decay 
228
.
2
92
Ce59
0
144 Pr+ 1 e
58 - decay

Zn29 65Cu++10e

0 + decay
3
K18 40Ar++1 0e
+ decay
144
.
3
65
.
4
40
.
5
7
7
.
6

19
Be 4
Be+ 
decay
4
n+ 92
1
7. 0 2 3 5 U   9 2
R n   8924 2 3 6 U 
1n
55
+2 4+3
Cs+37 PoRb
He 0
decay
222
141
8.
86
I  5129
4
Xe+
129
953
.
10.
Pu92
U+2
He decay
239
4
94
15
11.
-decay
0
1 e
235
O 15 7N++1 0e
+
decay
8
Fe27 59Co+1
0e
59
12.
T h   8Ra+
8
2 4He
Tc 4 3
99
Tc + 
234
9 9 90
a.
c.
230
43
7
3
b.
26
11
d.
6
C+ 1 0 e 5 11 B
H+ Li 22 4He or 4 8Be
1
13.
Fission
218

1
Be+0 n 21 H + 2 4He or 1 1H +1 3H+2 4He
1
7
14.
2

4
246
Cm+ 6 C  1 0 2
No +40
12
254
15.
96
1n
Cf + 5 B  1 0 3
Lr +20
98
250
10
16.
258
1n