1. Nuclear Decay

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

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

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

5. 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

6. Radioactive Decay Radioactive decay results in the emission of either:
an alpha particle (a),
a negative beta particle (electron) (b-),
a positive beta particle (positron) (b+),
or a gamma ray (g).
In a nuclear reaction the MASS and ATOMIC NUMBER must be the SAME on both sides of the equations

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

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

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

10. U + He U + Th Write the equation for the alpha decay of Uranium-23492 + Th
230 90

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

12. X Y + e Beta Emission A Z Z + 1 -1 beta particle (electron)
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
Z + 1 + e -1
beta particle
(electron)
proton stays
in nucleus

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

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

15. C + C N + e Write the equation for the beta emission of carbon-14 147 + e -1

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

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

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

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

20. Ni + Ni e + Co Write the equation for electron capture of nickel-59 5928 e -1 + Co 27

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

22. X Y + e Positron Emission A Z Z - 1 +1 positron mass stays in nucleus
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
Z - 1 + e +1
positron
mass stays
in nucleus

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

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

25. O + O N + e Write the equation for the positron emission of oxygen-167 + e +1

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

27. Gamma Decay
When atoms decay by emitting a or b 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.
Gamma rays are high energy radiation
Gamma rays are not charged particles like a and b particles.
There is no change in mass or atomic number X A Z + g

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

29. Nuclear Stability Not all isotopes are radioactive
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

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

31. 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

32. Chain Reaction Each reaction allows multiple other reactions to occur
Controlled vs Uncontrolled

33. 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

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