Page 211 - Physics Form 5 KSSM_Neat

Equation for Beta (b) Decay CHAPTER 6

Beta particle is a fast-moving electron. During beta decay, a neutron in an unstable nucleus
decomposes into one proton and one electron as shown below: Nuclear Physics

1 n ˜ p + e
1
0
0 1 –1
KEMENTERIAN PENDIDIKAN MALAYSIA
The resulting proton remains in the nucleus while the electron is emitted with high kinetic
energy as b-particle as shown in Figure 6.3.
The general equation for b-decay is
as follows:
A X ˜ A Y + e
0
Z Z + 1 –1 After b-decay, the proton number for the
b-particle daughter nucleus becomes Z + 1 but the
nucleon number, A does not change.
+ + + +
+ + + + + + Example of a b-decay:
+ + + + +
+ + + + + + + + + +
24
0

+ + + + + + 24 Na ˜ Mg + e
11 12 –1
Parent Daughter Beta
nucleus nucleus particle
Figure 6.3 Beta decay
Equation for Gamma (g) Decay
Gamma rays are high-frequency electromagnetic wave. During gamma decay, an unstable nucleus
releases its excess energy to become more stable, as shown in Figure 6.4. Gamma rays have no
mass and are neutral (not charged).

The general equation for g-decay is as follows:
A X ˜ X + g
A

Z Z After g-decay, there are no changes in the proton
g-ray number and nucleon number for the nucleus.
The nucleus is less energetic after gamma decay.
+ + + +
+ + + + + + + + Example of a g-decay:
60
+ + + + + + + + + + 60 Co ˜ Co + g

+
+ + + + 27 27
Radioactive nucleus Nucleus with Gamma ray
Sinar gama
Nukleus induk
Nukleus
in an excited state less energy
dalam keadaan
anak
teruja
Figure 6.4 Gamma decay
During a radioactive decay, some nuclei can emit more than one radiation. For example,
during the disintegration of uranium-234, its nucleus emits α-particle and g-ray. Examples of its
decay equation and a simpler decay equation are as follows:
Decay equation: Simpler decay equation:
4
234 U ˜ 230 Th + He + g a, g

92 90 2 234 U ˜ 230 Th
92
90
LS 6.1.1 201