Name __________________
Chapter 22 Nuclear Chemistry
History – not in textbook from the nuclear engineering dept. at NCSU
1895 x-rays discovered By Roentgen *1898 Curies*
1905 E=mc2
1913 Bohr model of atom *Quantum* perfect calculations for H atom
1919 1st nuclear Reaction
1932 Neutron discovered by Chadwick
1934 artificial radioactivity
1939 Fission discovered by Lise Meitner (story in textbook)
1942 1st controlled chain Reaction
Enrico Fermi University of Chicago
Atomic pile; composed of Uranium & graphite
Manhattan Project  atom bomb
Oak Ridge, UC Berkeley with Dr. Oppenheimer
* U & Th then Po, Ra discovered
Note: Germans needed dry ice to do research on nuclear fusion (They said no to Nazis)
p.1
Chapter 22
Nucleus & Radioactivity p.701
Nuclear Chemistry
Mass  A
Protons + Neutrons  14
Atomic #  Z
Protons  6
Introduction:
Chemistry is determined by valence e- with a positive nucleus that keeps e- bound in
atoms & compounds
Nucleus: very small, very dense
Nuclear Radius 10-13 cm vs. of atomic radius 10-8 cm
Distance
Size: can be related as…
Difference in distance between - Ping Pong Ball as the nucleus
and the furthest electron from the nucleus at 0.5km or 0.3mi which is about the length
of a football field
Density- Nucleus is Very Dense
If 1.6 *1014 g/cm3 were the density of a ping pong ball, it would weigh 2.5 billion tons
Energy
Nuclear Reaction yields 106 times more energy than any chemical Reaction
Originally Greek atom thought atoms to be indivisible, now know, e-, p and n and more
recent subatomic particles include quarks (not studied here)
Nucleon (a particle in the nucleus can be either a n or p)
Nuclides are isotopes e.g.
p.2
C-12 C-13 C-14
Nuclear Particles p. 706
p.713 protection and exposure
Alpha particle,
Beta particle, an electron,
Beta-plus particle, a positron (not studied here)
Neutron
While all particles
produced by the decay
of an atomic nucleus have
the energy to penetrate
substances, some particles
have much more energy
than others.
Types of Particles
alpha (helium nuclei)
beta (electrons)
gamma-radiation
Symbol
4
2He
0
-1e
Necessary Protection
air, paper
plastic, foil
lead, concrete
p. 3
p.701 and 705 Radioactive Decay:
Smaller (more stable) atoms have P:N ratio of 1:1 more stable
Larger atoms (can be more unstable) have P:N ratio of 1:1.5, these are
unstable and start to fall apart i.e. are radioactive.
Transmutation: identity changes because nucleus changes (i.e. the # Protons)
Nuclear Reactions nucleus changes
Nuclear equations must be balanced.
To balance nuclear equations, follow these rules:
1. Mass number is conserved in a nuclear change.
2. Electric charge is conserved in a nuclear change.
p.4
p. 705 Radioactive Decay (sometimes change mass # of an element but the total mass
before and after the decay would be the same) do the sample problems on p. 704
1) Alpha Decay 42He – (α, not a)
Example:
92 U
 42He + 23490Th
230
90Th
 42He + 22688Ra
238
2) Beta decay occurs when a neutron splits into a proton and an electron that
leaves the nucleus (emitting an electron i.e. beta particle)
234
90Th
131
53I
 23491Pa + 0-1e
 13154Xe + 0-1e
3) Spontaneous Fission: split into 2 lighter nuclides
Some elements do not change mass, but do change atomic #
Neutron bombards the nuclide
U23592 
92
36Kr
+ 14156Ba + 3 neutrons
Neutron
p. 710 Radioactive Decay Series of radium 226
and the Fermi lab (1st controlled nuclear reaction -1942 enabled the making of the
atom bomb) on p. 711
p.5
Practice a few problems
a. lead –214 decays by beta emission
b. bismuth- 214 decays by beta emission
c. polonium-214 decays by alpha emission
Fusion v.s. Fission p. 717
Fusion:
Deuterium 21H
4
2He
+
Tritium 31H
Fusion occurs naturally on the sun
Fusion can only occur in plasma.
Plasma: low density superheated gas
Example: Hydrogen Bombs
Fusion – occurs in sun and stars
4 11H  24He + 2 +10e
energy
When the 4 pieces fuse, energy is released.
p.6
+ neutron + ENERGY!!!!!!!
Fission: split into more stable nuclei of intermediate mass occurs spontaneously or by
neutron bombardment
U 235 + slow 01n  becomes unstable & splits
Fission:
U23592
92
36Kr
Neutron
Starts
Chain
Reaction
Example: Atomic Bomb
p.7
+ 14156Ba + 3 neutrons + **Energy Released**
Nuclear Reactors have controlled fission chain Reactions to get Energy or Radioactive
nuclides - Nuclear Power: stopped by cadmium rods which absorbs neutrons
p. 718 Nuclear Power Plants Reaction  heat  hot H2O  electricity in turbines
U-235 used often
Shielding: absorb radiation especially with Cd rods which absorb neutrons or Lead
shields stop radiation (does not pass through the lead shield)
Fuel: U-235
Control Rods- neutron absorbing
Moderator: slows fast neutron  to be slow
Coolant: H2O i.e. Cooling Towers like Shearon Harris plant in Apex
Nuclear Chemistry Uses p.715
1. Power
2. Medicine
a) PET scan
b) MRI
c) X-Rays
d) Tracers
e) Radiation Therapy
3. Forensics: Hair, nails, As, gamma spectrometer at NCSU
4. Toxic Metal Waste: Hg, Se
5. Space: Nuclear Batteries
p. 9
p. 714 Radiation Detection:
a) Film Badges
b) Geiger Counters
c) Scintillation Counters
Nuclear Waste :
a.
b.
c.
d.
e.
103 Nuclear Reactors (power)
Refuel every 12-24 months
Some plants ship spent fuel
By 2010, government said “replace power plant”
**Yucca mntn*
Chernobyl: nuclear disaster in the Ukraine- released 7000 kg of radioactive decay.
Damage was detected as far as Washington, DC.
Geiger Counter: an instrument used to measure the level of radiation.
Dosimeter: personal radiation device
Scientists make radioactive isotopes: can be used for….
a) Medicine
b) Radiation therapy for cancer uses
c) X-rays and Gamma Rays
(From Cobalt-60 and Cesium-137) & Research  P32 and S35
Tracers: radioactive isotopes, natural and manufactured. Chemical tracers follow
certain metabolic processes in the body.
Irradiation: radioisotopes used to treat food so that it can be stored without
refrigeration for a long time.
p. 10
Half Life p. 708 do problems on p. 709
Each radioactive element breaks down at a specific rate.
The time required for one half of a sample to decay is known as the half-life of that
substance.
The half-life is constant regardless of what you do to that element.
Some elements decay to a stable nucleus in less than 1 second. Others may require
millions of years.
Carbon-14 (isotope of carbon with neutrons)
It is found in all living things. It is absorbed in CO2. The half-life is 5730 years. By
measuring the percentage of C-14 in a fossil or skeleton, scientists can determine
the age of the material.
This is called radioactive dating.
Half-life: time required to decay ½
Example: ½ atoms to transform into something else
20g 10g 5g2.5g
1(1/2 life)
(1/2)3 * 20g
(1/8) * 20g= 2.5g
2nd 1/2L
3rd 1/2L
Graphs:
No
Parents to
daughters
Problems
½ No
¼ No
1/8 No
0
t½
2t ½
3t ½
4t ½
No =original amount of substance
p. 11
Practice Problems
Strategy:
1. Determine the fraction of the isotope that is remaining.
2. Use the remaining fraction of the isotope, to determine how many
half-lives have passed? Ie. If there is 1/8 of a sample left then:
½ X ½ X ½ = 1/8 - 3 half-lives have passed.
3. Multiply the number of half-lives that have passed by the half-life.
Ie. 3 X 200 years.
1. The half-life of iodine-131 is 8.1 days. How long will it take for threefourths of a sample of iodine-131 to decay?
2. A sample of Strontium-90 is found to have decayed to one-eighth of its
original amount after 87.3 years. What is the half-life of strontium-90?
3. The ratio of carbon-14 to carbon-12 is a prehistoric wooden artifact is
measured to be one-eighth of the ratio measured in a fresh sample of
wood from the same region. The half-life of carbon-14 is 5,715 years.
Determine its age.
4. Health officials are concerned about radon levels in homes. The half-life
of radon-222 is 3.82 days. If a sample of gas contains 4.38 micrograms
of radon-222, how much will remain in the sample after 15.2 days?
p. 12