RADIO DECAY FROM WEB

1. Komperda
 TRUE OR FALSE
1. As the sample of radioactive
decays, it half life decreases.

2. Komperda
 TRUE OR FALSE
2. As the half life increasers the mass
of the radioactive material increases

3. Komperda
 TRUE OR FALSE
3. The time required for half a
radioactive sample to disintegrate is
called half life.

4. Komperda
 TRUE OR FALSE
5. Half life is constant to all
radioactive substance

5. Komperda
 TRUE OR FALSE
4. Decay constant defined as the
fraction of the number of atom
decay in a unit time.

6. 
Komperda
Nuclear Decay

7. Komperda
The Atom- Review
•The atom consists of two parts:
1. The nucleus which contains:
2. Orbiting electrons.
protons
neutrons
•Atom of different elements contain different numbers
of protons.
•The mass of an atom is due to the number of protons
and neutrons.

8. Komperda
X
A
Z
Mass number
Atomic number
Element symbol
= number of protons + number of neutrons
= number of protons
Isotope Symbol Review
A = number of protons + number of neutrons
Z = number of protons
A – Z = number of neutrons
**Number of neutrons = Mass Number – Atomic Number**

9. Komperda
U
235
92
U
238
92
Fill in the chart for each isotope
A
Z
Number of protons
Number of neutrons
A
Z
Number of protons
Number of neutrons
235
92
92
143
92
92
238
146
Isotopes of any particular element contain the same
number of protons, but different numbers of neutrons.

10. Komperda
•Most of the isotopes which occur naturally are stable.
•A few naturally occurring isotopes and all of the man-
made isotopes are unstable.
•Unstable isotopes can become stable by releasing
different types of particles.
•This process is called radioactive decay and the
elements which undergo this process are called
radioisotopes.
•The products of this decay are called daughter isotopes

11. Komperda
Radioactive decay results in the emission of either:
• an alpha particle (α),
• a negative beta particle (electron) (β−
),
• or a gamma ray (γ).
Radioactive Decay
• a positive beta particle (positron) (β+
),
In a nuclear reaction the MASS and ATOMIC NUMBER
must be the SAME on both sides of the equations

12. Komperda
An alpha particle is identical to that of a helium nucleus.
It contains two protons and two neutrons.
Alpha Decay
X
A
Z
Y
A - 4
Z - 2
+ He
4
2
unstable atom
more stable atom
alpha particle

13. Komperda
Alpha Decay
Ra
226
88
Rn
222
86
He
4
2
+
Loss of 2 protons & 2 neutrons:
Atomic # decreases by 2
Mass # decreases by 4

14. Komperda
X
A
Z
Y
A - 4
Z - 2
+ He
4
2
Write your own Alpha Decay
Rn
222
86
+
Y
A
Z
He
4
2
What is Y?
Rn
222
86
He
4
2
+
Po
218
84
He
4
2

15. Komperda
U
234
+
Write the equation for the alpha
decay of Uranium-234
He
4
2
U
234
92
+
Th
230
90
He
4
2

16. Komperda
X
A
Z
+
Pb
214
82
He
4
2
Find the missing starting material
He
4
2
+
Pb
214
82
He
4
2
Po
218
84

17. Komperda
Beta Emission
A beta particle is a fast moving electron which is emitted
from the nucleus of an atom undergoing radioactive decay.
Beta emission occurs when a neutron changes into a
proton and an electron.
X
A
Z
Y
A
Z + 1
+ e
0
-1
beta particle
(electron)
proton stays
in nucleus

18. Komperda
Beta Emission
Po
218
84
e
0
-1
At
218
85
+
Neutron splits emitting negative
particle leaving a proton.
•Atomic # increases by 1
•Mass # stays the same
(electrons have no mass)

19. Komperda
X
A
Z
Y
A
Z + 1
+ e
0
-1
Write your own Beta Emission
What is Y?
Th
234
90
Y
A
Z
+ e
0
-1
Th
234
90
Pa
234
91
+ e
0
-1

20. Komperda
C
14
+
Write the equation for the beta
emission of carbon-14
C
14
N
14
7
+ e
0
-1

21. Komperda
X
A
Z
Bi
214
83
+ e
0
-1
Find the missing starting material
Pb
214
82
Bi
214
83
+ e
0
-1

22. Komperda
Electron Capture is the opposite of Beta Emission
Electron Capture
X
A
Z
e
0
-1
+ Y
A
Z-1
The capture of the electron allows a proton to turn into
a neutron

23. Komperda
Electron Capture
Po
218
84
e
0
-1
At
218
85
+
Capture negative particle,
forming a neutron from a proton
•Atomic # decreases by 1
•Mass # stays the same
(electrons have no mass)

24. Komperda
Write your own Electron Capture
What is Y?
X
A
Z
e
0
-1
+ Y
A
Z-1
Ar
37
18
e
0
-1
+ Y
A
Z-1
Ar
37
18
e
0
-1
+ Cl
37
17

25. Komperda
Ni
59
+
Write the equation for electron
capture of nickel-59
Ni
59
28
e
0
-1
+ Co
59
27

26. Komperda
Find the missing starting material
X
A
Z
e
0
-1
+ C
14
6
N
14
7
e
0
-1
+ C
14
6

27. Komperda
Positron Emission
A positron is like an electron but it has a positive charge.
During positron emission a proton changes into a
neutron and the excess positive charge is emitted.
X
A
Z
Y
A
Z - 1
+ e
0
+1
positron
mass stays
in nucleus

28. Komperda
Positron Emission
Po
218
84 e
0
+1
At
218
85
+
Proton splits emitting positive particle
leaving a neutron.
•Atomic # decreases by 1
•Mass # stays the same
(positrons, like electrons, have no mass)

29. Komperda
X
A
Z
Y
A
Z - 1
+ e
0
+1
Write your own Positron Emission
What is Y?
B
8
5
Y
A
Z
+ e
0
+1
B
8
5
Be
8
4
+ e
0
+1

30. Komperda
O
16
+
Write the equation for the positron
emission of oxygen-16
O
16
N
16
7
+ e
0
+1

31. Komperda
X
A
Z
Cu
66
29
+ e
0
+1
Find the missing starting material
Zn
66
30
Cu
66
29
+ e
0
+1

32. Komperda
Gamma Decay
•Gamma rays are not charged particles like α and β
particles.
•Gamma rays are high energy radiation
•When atoms decay by emitting α or β particles to form a
new atom, the nuclei of the new atom formed may still
have too much energy to be completely stable. These
atoms will emit gamma rays to release that energy.
•There is no change in mass or atomic number
X
A
Z
X
A
Z
+ γ
0
0

33. Komperda
Summary
Reaction What happens? Mass # Atomic #
Alpha Decay
α
Lose Helium Nucleus -4 -2
Beta Decay
β-
Lose electron from nucleus
(neutron turns into proton)
No change +1
Electron Capture Gain electron in nucleus
(proton turns into neutron)
No change -1
Positron Emission
β+
Lose positron
(proton turns into neutron)
No change -1
Gammy Decay
γ
Emit high energy gamma ray No change No change

34. Komperda
Nuclear Stability
 The strong nuclear force holds all nuclei together
 Otherwise protons would repel each other
 Neutrons space out protons and make nucleus stable
 Not all isotopes are radioactive
 Only unstable nuclei decay
 In smaller atoms stable isotopes have equal numbers of
protons and neutrons
 In larger atoms stable isotopes will have more neutrons
than protons
 Too many or too few neutrons makes the nucleus unstable

35. Komperda
Nuclear Stability Graph
Dark band = stable nucleus
Areas off line = radioactive

36. Komperda
Fission
 Fission is when a nucleus splits
 This is what happens in
nuclear power plants
 Neutrons emitted during
fission reactions can cause
other fission reactions
 This is a chain reaction
 In a nuclear reactor the
chain reaction is controlled
with control rods

37. Komperda
Chain Reaction
 Each reaction
allows multiple
other reactions
to occur
 Controlled vs Unco

38. Komperda
Fusion
 When two or more elements fuse (combine) to form one
new heavier element
 The energy released by the sun and all stars is due to fusion
reactions in the core
 This process releases more energy than fission
 Fusion reactions are hard to contain because the reactants
are a plasma and at very high temperatures, no solid
material can contain a plasma

39. Komperda
Fission Fusion
Nuclei combine
Nucleus splits
End product is
heavier than
reactants
End product is
lighter than
reactants
Energy is
released
LOTS of energy
released
Can’t contain
reaction
Reaction can be
harnessed
Nuclear
Change