1. Nuclear Reactions

2. Natural Transmutation
1 term on reactant side
original isotope (naturally radioactive)
2 terms on product side
emitted particle
new Isotope
Happens all by itself (spontaneous)
Not affected by anything in environment

3. Natural Transmutation
16N  0e O 7 -1 8
2 terms on product side
1 term on reactant side

4. Artificial Transmutation
cause to happen: smash particles
into one another
2 terms on reactant side
original Isotope (non-radioactive)
particle that hits it
neutron, proton, or -particle
product side: usually 2 terms

5. Artificial Transmutation
27Al He  30P + 1n 15 13 2
original isotope or
target nucleus
“bullet”
- thing hits isotope

6. Artificial Transmutation
27Al + 4He  30P + 1n
all these equations have 2 reactants! 13 2 15
14N + 4He  17O + 1H 1 2 8 7
75As + 4He  78Br + 1n 2 35 33
37Cl + 1n  38Cl 17 17

7. Bombarding with protons or 
protons & -particles have positive charge and mass
do some damage when hit target nucleus
must be accelerated to high speeds to overcome repulsive forces between nucleus & particle (both are +)

8. What is an accelerator? vacuum chamber (usually long pipe)
surrounded by vacuum pumps, magnets, radio- frequency cavities, high voltage instruments & electronic circuits
inside pipe particles are accelerated to very high speeds then smashed into each other

9. splitting heavy nucleus into 2 lighter nuclei
Fission Reaction
splitting heavy nucleus into 2 lighter nuclei
requires critical mass of fissionable isotope
controlled: nuclear reactor
uncontrolled: bomb

10. Fission Fission = Division reactant side: 2 terms
1 heavy isotope (examples: U-235 or Pu-239)
bombarding particle – usually a neutron
product side: at least 2 terms
2 medium-weight isotopes
1 or more neutrons
huge amount energy released
Fission = Division

11. Fission 235U + 1n  91Kr + 142Ba + 31n + energy 56 92 3692 36
235U + 1n  72Zn + 160Sm + 41n + energy 62 92 30
more than 200 different product isotopes identified from fission of U-235
small amount of mass is converted to energy according to E = mc2

12. Fusion 2H + 3H  4He + 1n + energy reactant side has 2 small nuclei:
H + H; H + He; He + He
product side:
1 nucleus (slightly larger; still small) and maybe a particle
source of sun’s energy
2 nuclei unite
2H + 3H  4He + 1n + energy 2 1 1

13. CERN 27 kilometer ring particles travel just below speed of light
10 hrs: particles make 400
million revolutions of ring

14. FermiLab
4 miles in circumference!

16. Balancing Nuclear Equations

17. Nuclear Equations - tasks
identify type (4 types):
natural transmutation
artificial transmutation
fission
fusion
balance to find unknown term

18. Natural Transmutation – ID
1 term on reactant side
starting isotope
2 terms on product side
ending isotope & emitted particle
type of particle emitted characteristic
of isotope – Table N

19. Nuclear Equations
to balance: use conservation of both atomic number & mass number
mass number = left superscript
atomic number = left subscript

20. Balancing Nuclear Equations
16N  0e O -1 7 8
conservation of mass number: 16 =
conservation of atomic number: 7 =

21. Writing Equations write equation for decay of Thorium-232
use Table N to find decay mode: α
write initial equation:
232Th  4He + X 90 2
figure out what element it turned into

22. What’s under the hat?
Little cats X, Y, & Z!

23. Write an equation for the α decay of Th-232
232 Th  4He + YX
what’s X? 95 2 Z

24. so Y = 228 232 = 4 + Y conservation of mass number:
232Th  4He X Y Z 90 2
conservation of mass number:
sum mass numbers on left side must
= sum mass numbers on right side

25. so Z = 88 90 = 2 + Z conservation of atomic number:
232Th  4He + 228X 2 90 Z
90 = Z
so Z = 88
conservation of atomic number:
sum of atomic numbers on left side must
= sum of atomic numbers on right side

26. 232Th  4He + 228X 90 2 88
use PT to find X:
X = Ra
232Th  4He + 228Ra 90 2 88

27. Radioactive Decay Series
sometimes 1 transmutation isn’t enough to achieve stability
some radioisotopes go through several changes before achieve stability (no longer radioactive)

28. radioactive decay series: Th-232 transmuting to Pb-208

29. β C  14N + 0e 6 7 -1
beta
β F  18O + 0e
positron 9 8 +1

30. How does the mass number or atomic number change in α,β or γ decay?
go to Table N:
find isotope that decays by α or β decay
write equation
see how mass number (or atomic number) changes
22688Ra  42 + X so X has to be 22286X
α decay of Ra-226:
mass number decreases by 4
atomic number decreases by 2

32. So how do you know if an element is radioactive or not?
Element (atom)
UNSTABLE
STABLE
n/p ratio
>1.5:1
1:1 up to 1.5:1
atomic number
83 and above
≤ 82
radioactive
yes
not
the key is the proton to neutron ratio