Nuclear chemistry

1. Nuclear ChemistryNuclear Chemistry

2. RadioactivityRadioactivity
•One of the pieces of evidence for the fact One of the pieces of evidence for the fact
that atoms are made of smaller particles that atoms are made of smaller particles
came from the work of Marie Curie came from the work of Marie Curie
(1876-1934). (1876-1934).
•She discovered radioactivity: the She discovered radioactivity: the
spontaneous disintegration of the nucleus spontaneous disintegration of the nucleus
of some elements into smaller pieces.of some elements into smaller pieces.

3. Nuclear Reactions vs. Normal Nuclear Reactions vs. Normal
Chemical ChangesChemical Changes
•Nuclear reactions involve the nucleusNuclear reactions involve the nucleus
•The nucleus loses particles, and protons The nucleus loses particles, and protons
and neutrons are rearrangedand neutrons are rearranged
•The disintegration of the nucleus releases The disintegration of the nucleus releases
a tremendous amount of energy that a tremendous amount of energy that
holds the nucleus together – called holds the nucleus together – called
binding energybinding energy
•““Normal” Chemical Reactions involve Normal” Chemical Reactions involve
electrons, not protons and neutronselectrons, not protons and neutrons

5. Types of RadiationTypes of Radiation
e
0
1-
He
4
2
• Alpha (Alpha (άά) – a positively ) – a positively
charged helium isotopecharged helium isotope - - we usually we usually
ignore the charge because it involves electrons, ignore the charge because it involves electrons,
not protons and neutronsnot protons and neutrons
•Beta (Beta (ββ) – an electron) – an electron
•Gamma (Gamma (γγ) – pure energy; ) – pure energy;
called a ray rather than a called a ray rather than a
particleparticle
g
0
0

6. 6
Alpha Decay
When a radioactive
nucleus emits an
alpha particle, a
new nucleus forms
that has:
•a mass number that
is 4 less than that of
the initial nucleus.
•an atomic number
that is decreased by
2.

7. 7
Alpha Decay Nuclear Equation
Copyright © 2005 by Pearson Education, Inc.Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin CummingsPublishing as Benjamin Cummings

8. In a balanced nuclear equation, the sum of the
mass numbers and the sum of the atomic
numbers for the nuclei of the reactant and the
products must be equal.
MASS NUMBERS
Total = 251 = 251
251
Cf
247
Cm

+
4
He

98 96 2
Total = 98 = 98
ATOMIC NUMBERS
Balancing Nuclear Equations

9. Equation for Alpha Decay
Write an equation for the alpha decay of
222
Rn.
STEP 1 Write the incomplete equation

222
Rn ?s +
4
He

86 2
STEP 2 Determine the mass number 222 – 4 = 218
STEP 3 Determine the atomic number 86 – 2 = 84
STEP 4 Determine the symbol of element 84 = Po
STEP 5 Complete the equation

222
Rn
218
Po +
4
He

86 84 2

10. 10
Beta Decay
A beta particle
•is an electron
emitted from the
nucleus.
•forms when a
neutron in the
nucleus breaks
down.
1
n
0
e +
1
H
0 -1 1

11. STEP 1 Write an equation for the decay of
42
Potassium,a beta emitter.

42
K new nucleus +
0
e

19

-1
STEP 2 Mass number : (same) = 42
STEP 3 Atomic number: 19 + 1 = 20
STEP 4 Symbol of element 20 = Ca
STEP 5
42
K
42
Ca +
0
e

19 20 -1
Writing An Equation for Beta Decay

12. Other Nuclear ParticlesOther Nuclear Particles
e
0
1+
n
1
0
• NeutronNeutron
• Positron – a positive Positron – a positive
electronelectron
• Proton – usually referred Proton – usually referred
to as Hydrogento as Hydrogen
+1+1
• Any other elemental Any other elemental
isotopeisotope
H
1
1

15. Half Life
The time required for half of the nuclei in a The time required for half of the nuclei in a
sample of a specific isotope to undergo sample of a specific isotope to undergo
radioactive decay.radioactive decay.

16. Radioactive
Parent
Stable Daughter Half life
Potassium 40 Argon 40 1.25 billion yrs
Rubidium 87 Strontium 87 48.8 billion yrs
Thorium 232 Lead 208 14 billion years
Uranium 235 Lead 207 704 million years
Uranium 238 Lead 206 4.47 billion years
Carbon 14 Nitrogen 14 5730 years
Half Lives for Radioactive Elements

17. Half Life and radioactive dating

18. Half-LifeHalf-Life
Decay of 20.0 mg of Decay of 20.0 mg of
1515
O. What remains after 3 O. What remains after 3
half-lives? After 5 half-lives?half-lives? After 5 half-lives?

19. Learning Check!
The half life of I-123 is 13 hr.
How much of a 64 mg sample of
I-123 is left after 39 hours?

20. In gamma radiation
•energy is emitted from an unstable
nucleus, indicated by m following the
mass number.
•the mass number and the atomic
number of the new nucleus are the
same.

99m
Tc
99
Tc + g
43 43
Gamma (g) Radiation

21. In position emission,
•a proton is converted to a neutron and a
positron.

1
p
1
n +
0
e
1 0 +1
•the mass number of the new nucleus is
the same, but the atomic number
decreases by 1.

49
Mn
49
Cr +
0
e
25 24 +1
Positron Emission

22. Why radiation is dangerous
Radiation ionizes atoms in cell tissue and causes Radiation ionizes atoms in cell tissue and causes
chemical reactions akin to decomposition / chemical reactions akin to decomposition /
combustion. combustion.
disrupts nucleotide sequences (your DNA is mutated)disrupts nucleotide sequences (your DNA is mutated)

23. Why radiation is dangerousWhy radiation is dangerous

24. Measuring Radiation
•How radioactive a substance is refers to the How radioactive a substance is refers to the
number of nuclear disintegrations per second number of nuclear disintegrations per second
that occur in a sample. that occur in a sample.
•SI unit is the Becquerel (Bq) which is 1 SI unit is the Becquerel (Bq) which is 1
disintegration/seconddisintegration/second
•The older unit, the Curie(Ci) :The older unit, the Curie(Ci) :
1 Ci = 3.7 x 101 Ci = 3.7 x 10
1010
disintegrations per second disintegrations per second

25. Measuring Radiation
•The The 'rad'rad' is used to describe the energy quantity ' is used to describe the energy quantity
or dose of radiation absorbed. or dose of radiation absorbed.
•radrad (rd) stands for “radiation absorbed dose” (rd) stands for “radiation absorbed dose”
•One One radrad defined as 10 defined as 10
-5-5
J/g of material. J/g of material.

26. Measuring Radiation Damage
•The rad does not account for the kind of damage The rad does not account for the kind of damage
done, only for how much radiation goes in.done, only for how much radiation goes in.
•To take into account this fact the REM was To take into account this fact the REM was
derivedderived
•To find the dose in REMS the dosage in rads is To find the dose in REMS the dosage in rads is
multiplied by a conversion factor that reflects the multiplied by a conversion factor that reflects the
effectiveness of the effectiveness of the kindkind of radiation causing the of radiation causing the
damagedamage

27. Dosage in REMS Biological Effect :

25 notable change in blood cell components 25 notable change in blood cell components

100 radiation sickness - nausea, vomiting, 100 radiation sickness - nausea, vomiting,
decrease in white blood cell count, diarrhea, decrease in white blood cell count, diarrhea,
dehydration, prostration, hemorrhaging and loss dehydration, prostration, hemorrhaging and loss
of hair of hair

200 the same as above but more pronounced in a 200 the same as above but more pronounced in a
shorter period of time shorter period of time
400 ½ of any population exposed to this dosage 400 ½ of any population exposed to this dosage
will be dead in 60 days will be dead in 60 days
600 all exposed to this level will be dead in one 600 all exposed to this level will be dead in one
week week

29. Chernobyl
Anyone near the Chernobyl plant when it melted Anyone near the Chernobyl plant when it melted
down received 400 rems also immediately. down received 400 rems also immediately.
The day after 1 rem/hr was found in the nearest The day after 1 rem/hr was found in the nearest
city. city.
Normal background radiation is 1,000 times lower Normal background radiation is 1,000 times lower
than thisthan this

31. Detecting radiation

32. Detecting radiation

33. Protection from radiation
•Wear lead infused suit.Wear lead infused suit.
•Keep your distance.Keep your distance.
• Inverse square law.Inverse square law.
• Intensity of radiation is inversely proportional Intensity of radiation is inversely proportional
to the square of the distance from the sourceto the square of the distance from the source

34. Nuclear Fuel
Uranium “Yellow Cake” UUranium “Yellow Cake” U
33OO
88

35. Fission
NeutronNeutron

36. Fission Chain Reaction

37. Representation of a fission process.

38. Nuclear FissionNuclear Fission

39. Diagram of a nuclear power plant.

41. Nuclear Fission & POWERNuclear Fission & POWER
•Currently about 103 Currently about 103
nuclear power plants in nuclear power plants in
the U.S. and about 435 the U.S. and about 435
worldwide.worldwide.
•17% of the world’s 17% of the world’s
energy comes from energy comes from
nuclear.nuclear.

42. Fusion
•A process by which multiple like-
charged atomic nuclei join
together to form a heavier nucleus

43. Nuclear Fusion
Fusion:
small nuclei combine
2
H +
3
H
4
He +
1
n +

1 1 2 0
Occurs in the sun and other stars
Energy

44. What radioactive isotope is produced
in the following bombardment of
boron?
10
B +
4
He ? +
1
n

5 2 0
Fusion

45. Nuclear Fusion
Fusion
•Excessive heat can not be
contained
•Attempts at “cold” fusion have
FAILED.
•“Hot” fusion is difficult to contain

46. Artificial Nuclear ReactionsArtificial Nuclear Reactions
New elements or new isotopes of known New elements or new isotopes of known
elements are produced by bombarding an elements are produced by bombarding an
atom with a subatomic particle such as a atom with a subatomic particle such as a
proton or neutron -- or even a much heavier proton or neutron -- or even a much heavier
particle such as particle such as
44
He and He and
1111
B.B.
Reactions using neutrons are called Reactions using neutrons are called
gg reactionsreactions because a because a gg ray is usually emitted. ray is usually emitted.
Radioisotopes used in medicine are often made Radioisotopes used in medicine are often made
by by gg reactionsreactions..

47. Artificial Nuclear ReactionsArtificial Nuclear Reactions
Production of radioactive Production of radioactive
3131
P for use P for use
in studies of P uptake in the body.in studies of P uptake in the body.
3131
1515P + P +
11
00n ---> n --->
3232
1515P + P + gg

48. Transuranium ElementsTransuranium Elements
Elements beyond 92 Elements beyond 92 (transuranium)(transuranium)
made starting with a made starting with a gg reactionreaction
238238
9292U + U +
11
00n ---> n --->
239239
9292U + U + gg
239239
9292U U ---> --->
239239
9393Np + Np +
00
-1-1bb

239239
9393Np Np ---> --->
239239
9494Pu + Pu +
00
-1-1bb

49. Nuclear Medicine: ImagingNuclear Medicine: Imaging
Thyroid imaging using Tc-99mThyroid imaging using Tc-99m

50. Food Food
IrradiationIrradiation
•Food can be irradiated with Food can be irradiated with gg rays from rays from
6060
Co or Co or
137137
Cs.Cs.
•Irradiated milk has a shelf life of 3 mo. Irradiated milk has a shelf life of 3 mo.
without refrigeration.without refrigeration.
•USDA has approved irradiation of meats USDA has approved irradiation of meats
and eggs.and eggs.