Nuclear Radiation
Natural Radioactivity Nuclear Equations Producing Radioactive Isotopes Half-Life Nuclear Fission and Fusion
1
Subatomic Particles
• Protons- plus charge
In the nucleus • Neutrons- neutral
• Electrons - negative charge Outside the nucleus
2
Radiation
• Radiation comes from the nucleus of an atom. • Unstable nucleus emits a particle or energy alpha
beta
gamma
3
Alpha Particle
Same as a helium nucleus (He)
4
2 He
or
Two protons Two neutrons
4
Beta Particle
An electron emitted from the nucleus
0
e or
1
A neutron in the nucleus breaks down 1 1 0 n H + e 0 1 -1
5
Gamma Radiation
• Pure radiation
• Like an X-ray but comes from the nucleus
6
Radiation Protection
• Shielding alpha – paper, clothing beta – lab coat, gloves gamma- lead, thick concrete • Limit time exposed • Keep distance from source
7
Radiation Protection
8
Balancing Nuclear Equations
In the reactants and products
Atomic numbers must balance and Mass numbers must balance
9
Alpha decay
10
Beta decay
234Th 90
234Pa 91
+ 0e
1
beta particle
11
Gamma radiation
No change in atomic or mass number
11B 5 11B 5
+
0 0
boron atom in a high-energy state
12
Learning Check NR1
Write the nuclear equation for the beta emitter Co-60.
13
Solution NR1
Write the nuclear equation for the Beta emitter Co-60.
60Co 27 60Ni 28
+
0e -1
14
Producing Radioactive Isotopes
Bombardment of atoms produces radioisotopes
= 60
59Co
= 60
56Mn
+ 1n
0
+
= 27
4H e
27
25
2
= 27
cobalt atom
neutron
manganese alpha radioisotope particle
15
Learning Check NR2
What radioactive isotope is produced in the following bombardment of boron?
10B
5
+ 4He
2
? +
0
1n
16
Solution NR2
What radioactive isotope is produced in the following bombardment of boron?
10B
5
+ 4He
2 7
13N
+
0
1n
nitrogen radioisotope
17
Half-Life of a Radioisotope
The time for the radiation level to fall (decay) to one-half its initial value
decay curve
initial
1 half-life 2
3
8 mg
4 mg
2 mg
1 mg
18
Examples of Half-Life
Isotope C-15 Ra-224 Ra-223 I-125 C-14 U-235 Half life 2.4 sec 3.6 days 12 days 60 days 5700 years 710 000 000 years
19
Learning Check NR3
The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 26 hours?
20
Solution NR3
t1/2 26 hours Amount initial = = = 13 hrs 2 x t1/2 64mg
Amount remaining = 64 mg x ½ x ½ = 16 mg
21
Nuclear Fission
Fission large nuclei break up
235U
92
+ 1n
0
139Ba
56
+
94Kr
36
+ 3 1n +
0
Energy
22
Fission
23
Nuclear Fusion
Fusion small nuclei combine
2H
1
+
3H
1
4He
2
+ 1n +
0
Energy
Occurs in the sun and other stars
24
Learning Check NR4
Indicate if each of the following are (1) Fission (2) fusion
A. B. C. D.
Nucleus splits Large amounts of energy released Small nuclei form larger nuclei Hydrogen nuclei react
Energy
25
Solution NR4
Indicate if each of the following are (1) Fission (2) fusion
A. B. C. D.
1 1+2 2 2
Nucleus splits Large amounts of energy released Small nuclei form larger nuclei Hydrogen nuclei react
26