1. Nuclear Chemistry
Unit 16

2. Introduction to Nuclear Chemistry
Nuclear chemistry is the study of the structure of and the they undergo.
atomic nuclei
changes

3. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays

4. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element

5. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons
May involve protons, neutrons, and electrons

6. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons
May involve protons, neutrons, and electrons
Associated with small energy changes
Associated with large energy changes

7. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons
May involve protons, neutrons, and electrons
Associated with small energy changes
Associated with large energy changes
Reaction rate influenced by temperature, particle size, concentration, etc.
Reaction rate is not influenced by temperature, particle size, concentration, etc.

8. The Discovery of Radioactivity (1895 – 1898):
Roentgen
found that invisible rays were emitted when electrons bombarded the surface of certain materials.
Becquerel accidently discovered that phosphorescent salts produced spontaneous emissions that darkened photographic plates
uranium

9. The Discovery of Radioactivity (1895 – 1898):
Marie Curie
isolated the components ( atoms) emitting the rays
– process by which particles give off
– the penetrating rays and particles by a radioactive source
uranium
Radioactivity
rays
Radiation
emitted

10. The Discovery of Radioactivity (1895 – 1898):
polonium
identified 2 new elements, and on the basis of their radioactivity
These findings Dalton’s theory of indivisible atoms.
radium
contradicted

11. The Discovery of Radioactivity (1895 – 1898):
same
Isotopes
– atoms of the element with different numbers of
– isotopes of atoms with nuclei (too / neutrons)
– when unstable nuclei energy by emitting to attain more atomic configurations ( process)
neutrons
Radioisotopes
unstable
many
few
Radioactive decay
radiation
lose
stable
spontaneous

12. Alpha radiation Composition – Alpha particles, same as helium nuclei
Symbol – Helium nuclei, He, α
Charge – 2+
Mass (amu) – 4
Approximate energy – 5 MeV
Penetrating power – low (0.05 mm body tissue)
Shielding – paper, clothing 4 2

13. Beta radiation Composition – Beta particles, same as an electron
Symbol – e-, β
Charge – 1-
Mass (amu) – 1/1837 (practically 0)
Approximate energy – 0.05 – 1 MeV
Penetrating power – moderate (4 mm body tissue)
Shielding – metal foil

14. Gamma radiation Composition – High-energy electromagnetic radiation
Symbol – γ
Charge – 0
Mass (amu) – 0
Approximate energy – 1 MeV
Penetrating power – high (penetrates body easily)
Shielding – lead, concrete

15. Review of Atomic Structure
Nucleus
Electrons
99.9% of the mass
1/10,000 the size of the atom
0.01% of the mass

16. Review of Atomic Structure
Nucleus
Electrons
99.9% of the mass
1/10,000 the size of the atom
0.01% of the mass
Composed of protons (p+) and neutrons (n0)
Composed of electrons (e-)

17. Review of Atomic Structure
Nucleus
Electrons
99.9% of the mass
1/10,000 the size of the atom
0.01% of the mass
Composed of protons (p+) and neutrons (n0)
Composed of electrons (e-)
Positively charged
Negatively charged

18. Review of Atomic Structure
Nucleus
Electrons
99.9% of the mass
1/10,000 the size of the atom
0.01% of the mass
Composed of protons (p+) and neutrons (n0)
Composed of electrons (e-)
Positively charged
Negatively charged
Strong nuclear force (holds the nucleus together)
Weak electrostatic force (because they are charged negatively

19. mass # atomic # neutrons atomic # mass #
Chemical Symbols
A chemical symbol looks like…
To find the number of , subtract the
from the
mass # 14 C
atomic # 6
neutrons
atomic #
mass #

20. not decompose 1 20 very stable 1:1 p+:n0 6 6
Nuclear Stability
not
Isotope is completely stable if the nucleus will spontaneously
Elements with atomic #s to are .
ratio of protons:neutrons ( )
Example: Carbon – 12 has protons and neutrons
decompose 1 20
very stable
1:1
p+:n0 6 6

21. 21 82 marginally stable 1:1.5 80 120 Nuclear Stability
Elements with atomic #s to are
ratio of protons:neutrons (p+ : n0)
Example: Mercury – 200 has protons and neutrons
marginally stable
1:1.5 80
120

22. > 82 unstable radioactive Uranium Plutonium
Nuclear Stability
> 82
unstable
Elements with atomic #s are
and
Examples: and
radioactive
Uranium
Plutonium

23. α He protons +2 mass 4 atomic 2 Atomic number balanced
Alpha Decay α
Alpha decay – emission of an alpha particle ( ), denoted by the symbol , because an α has 2 protons and 2 neutrons, just like the He nucleus. Charge is because of the
Alpha decay causes the number to decrease by and the number to decrease by .
determines the element. All nuclear equations are He 4 2
protons +2
mass 4
atomic 2
Atomic number
balanced

24. Alpha Decay
Example 1: Write the nuclear equation for the radioactive decay of polonium – 210 by alpha emission.
Step 3: Write the alpha particle.
Step 4: Determine the other product (ensuring everything is balanced).
Step 2: Draw the arrow.
Step 1: Write the element that you are starting with.
Mass #
210 Po 84
206 Pb 4 He 2 82
Atomic #

25. Alpha Decay
Example 2: Write the nuclear equation for the radioactive decay of radium – 226 by alpha emission.
Step 3: Write the alpha particle.
Step 4: Determine the other product (ensuring everything is balanced).
Step 2: Draw the arrow.
Step 1: Write the element that you are starting with.
Mass #
226 Ra 88
222 Rn 4 He 2 86
Atomic #

26. β electron e- e -1 electron no mass atomic 1
Beta decay β
Beta decay – emission of a beta particle ( ), a fast moving , denoted by the symbol or β has insignificant mass ( ) and the charge is because it’s an
Beta decay causes change in number and causes the number to increase by .
electron e- e -1
electron -1 no
mass
atomic 1

27. C e N Beta Decay 14 6 14 -1 7 Step 3: Write the beta particle.
Example 1: Write the nuclear equation for the radioactive decay of carbon – 14 by beta emission.
Step 3: Write the beta particle.
Step 4: Determine the other product (ensuring everything is balanced).
Step 2: Draw the arrow.
Step 1: Write the element that you are starting with.
Mass # 14 C 6 14 e -1 N 7
Atomic #

28. Zr e Nb Beta Decay 97 40 97 -1 41 Step 3: Write the beta particle.
Example 2: Write the nuclear equation for the radioactive decay of zirconium – 97 by beta decay.
Step 3: Write the beta particle.
Step 4: Determine the other product (ensuring everything is balanced).
Step 2: Draw the arrow.
Step 1: Write the element that you are starting with.
Mass # 97 Zr 40 97 e -1 Nb 41
Atomic #

29. electromagnetic γ no mass atomic always no omitted Gamma decay
Gamma rays – high-energy
radiation, denoted by the symbol
γ has no mass ( ) and no charge ( ). Thus, it causes change in or
numbers. Gamma rays almost accompany alpha and beta radiation. However, since there is effect on mass number or atomic number, they are usually from nuclear equations. γ no
mass
atomic
always no
omitted

30. Transmutation conversion radioactive–
the of one atom of one element to an atom of a different element
( decay is one way that this occurs!)
conversion
radioactive

31. Type of Radioactive Decay
Review
Type of Radioactive Decay
Particle Emitted
Change in Mass #
Change in Atomic #
Alpha
α He -4 -2
Beta
β e +1
Gamma γ 4 2 -1

32. half Half-life time Half-Life
is the required for of a radioisotope’s nuclei to decay into its products.
For any radioisotope,
# of ½ lives
% Remaining
100% 1
50% 2
25% 3
12.5% 4
6.25% 5
3.125% 6
1.5625%

33. Half-Life

34. Half-Life
For example, suppose you have 10.0 grams of strontium – 90, which has a half life of 29 years. How much will be remaining after x number of years?  
You can use a table:
# of ½ lives
Time (Years)
Amount Remaining (g) 10 1 29 5 2 58
2.5 3 87
1.25 4
116
0.625

35. initial mass mt = m0 x (0.5)n mass remaining # of half-lives
Half-Life
Or an equation!
initial mass
mt = m0 x (0.5)n
mass remaining
# of half-lives

36. Half-Life
Example 1: If gallium – 68 has a half-life of minutes, how much of a mg sample is left after 1 half life? ________
2 half lives? __________ 3 half lives? __________

37. Half-Life
Example 2: Cobalt – 60, with a half-life of 5 years, is used in cancer radiation treatments. If a hospital purchases a supply of 30.0 g, how much would be left after 15 years? ______________

38. Half-Life
Example 3: Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a mg sample will remain after days? ______________

39. Half-Life
Example 4: The half-life of polonium-218 is 3.0 minutes. If you start with 20.0 g, how long will it take before only 1.25 g remains? ______________

40. Half-Life
Example 5: A sample initially contains mg of radon After 11.4 days, the sample contains mg of radon Calculate the half-life.

41. changed nucleus Large energy
Nuclear Reactions
Characteristics:
Isotopes of one element are into isotopes of another element
Contents of the change
amounts of are released
changed
nucleus
Large
energy

42. Types of Nuclear Reactions
decay – alpha and beta particles and gamma ray emission
Nuclear emission of a or
Radioactive
disintegration
proton
neutron

43. Fission splitting two equal Chain split slowly nuclear reactors speed
Nuclear Fission
Fission
splitting
of a nucleus
- Very heavy nucleus is split into approximately fragments
reaction releases several neutrons which more nuclei
- If controlled, energy is released
(like in ) Reaction control depends on reducing the of the neutrons (increases the reaction rate) and
extra neutrons ( creases the reaction rate).
two
equal
Chain
split
slowly
nuclear reactors
speed
absorbing de

44. Nuclear Fission
- 1st controlled nuclear reaction in December st uncontrolled nuclear explosion occurred July
- Examples – atomic bomb, current nuclear power plants

45. Fusion combining light single + + no radioactive waste large start
Nuclear Fusion
Fusion
combining
of a nuclei
- Two nuclei combine to form a heavier nucleus
- Does not occur under standard conditions ( repels )
- Advantages compared to fission ,
- Disadvantages - requires amount of energy to , difficult to
- Examples – energy output of stars, hydrogen bomb, future nuclear power plants
light
single + +
inexpensive
no radioactive waste
large
start
control

46. Uses of Radiation
Radioactive _______________ - Carbon - ____ used to determine the ________ of an object that was once alive.
___________________________ of diseases – Iodine – 131 used to detect _________________ problems, technetium – 99 used to detect ___________ tumors and ____________ disorders, phosphorus – 32 used to detect __________ cancer.
Treatment of some _______________________ (cobalt – 60 and cesium – 137) – cancer cells are more ________________________ to radiation than normal, healthy cells

47. Uses of Radiation X-rays
Radioactive ________________ (used in research to _______ chemicals)
Everyday items – thorium – 232 used in ______________________, plutonium – 238 used in _______________________, and americium – 241 in ___________________________________