Radioactive Isotope

1
Radioactive Isotope

• Isotope which is unstable. It emits radiation
  changes into another kind of atom.

2
Transmutation Reaction

• When one kind of nucleus changes into another
  kind of nucleus.

3
Relationship between stability and energy

• As stability ?, energy ?.

4
Stability

• Depends on neutron to proton ratio.

5
Which elements are unstable?

• All the elements with atomic number gt 83 (or
  beyond Bismuth)

6
Types of Radiation

• Alpha, Beta, Gamma
• Separated by electric or magnetic fields.

7
Least penetration power

• Alpha radiation. Shielding can be paper or cloth.

8
Most penetration power

• Gamma radiation. Requires lead/concrete
  shielding.

9
2He or 2?

• Symbol for alpha radiation

4
4
10
2He or 2?

• Same as the nucleus of a helium atom

4
4
11
2He or 2?

• Mass 4 amu
• Charge 2

4
4
12
-1e or -1? or ?- or ?

• Symbol for beta particle

0
0
13
-1e or -1? or ?- or ?

• Fast moving electron originating from nucleus

0
0
14
-1e or -1? or ?- or ?

• Mass zero
• Charge -1

0
0
15
1e or 1? or ?

• Symbol for positron.

0
0
16
1e or 1? or ?

• Mass zero.
• Charge 1.
• Positive electron

0
0
17
0? or ?

• Symbol for gamma radiation.

0
18
0? or ?

• 0 mass
• 0 charge

0
19
0n or n

• Symbol for neutron

1
20
1H or 1p

• Symbol for proton

1
1
21
Alpha Decay

• Unstable nucleus emits an alpha particle. Atomic
  ? by 2. Mass ? by 4.

22
220Fr ? 4? 216At

• Unstable nucleus emits an alpha particle. Atomic
  ? by 2. Mass ? by 4.

2
85
87
23
220Fr ? 4? 216At

• Equation represents natural transmutation.
• 1 term on reactant side.

2
85
87
24
220Fr ? 4? 216At

• Balance nuclear equations using conservation of
  atomic number conservation of mass number.

4 216

220
2
85
87
2 85
87

25
of Half-Lives

• Elapsed time
• Length of H.L.

26
Half-Life Map
Mass Elapsed Time Fraction Remaining of Half Lives
Start mass 0 1 0
1 X H.L. ½ 1
2 X H.L. ¼ 2
3 X H.L. 1/8 3
4 X H.L. 1/16 4
27
Decay Mode

• Same as type of particle emitted

28
Average Atomic Mass

• Weighted average of the masses of the naturally
  occurring isotopes.

29
Artificial Transmutation

• Particle bullet hits target nucleus new
  isotope is produced.
• 2 terms on reactant side.

30
Artificial Transmutation
bullet
target

• 32S 1n ? 32P 1H

1
16
0
15
31
Artificial Transmutation

• Particle bullet may be proton or alpha
  particle. To react with a nucleus, must overcome
  repulsive forces by accelerating bullet to
  high speeds.
• Particle bullet may be a neutron. Neutrons
  have no charge, so no repulsive forces to
  overcome. No acceleration necessary.

32
Fission

• Fission is division.
• Large nucleus (U-235 or Pu-239) is split into 2
  medium sized nuclei by a neutron bullet. Excess
  neutrons a great deal of energy are also
  produced.

33
239Pu 1n ? 90Sr 147Ba 3 1n

• Fission

94
0
0
38
56
34
Fusion

• Fusion U for unite and U for sun.
• Very small nuclei (H He) are jammed together.
  Huge amounts of energy are released.

35
1H 2H ? 3He

• Fusion

1
1
2
36
Identify each of the rxns
fission

• 1n 235U ? 142Ba 91Kr 3 1n energy
• 59Co 1n ? 60Co
• 3He 1H ? 4He 0e
• 14C ? 14N 0e

0
92
56
36
0
Artificial transmutation
27
0
27
fusion
1
2
2
1
Natural transmutation
6
7
-1