What do they have in common?

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What do they have in common?
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Nuclear Chemistry
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Nuclear Reactions

• Involve the nucleus
• Radioactivity is the spontaneous emission of
  radiation from an atom

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Nuclear Stability

• Most atoms have a stable nucleus
• A strong nuclear force holds protons and neutrons
  together
• Neutrons act as the glue holding the protons
  together

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Belt of Nuclear Stability
There seems to be a ratio of protons to neutrons
that increase the chances that an atom will be
stable.
Figure 18.1 The Zone of Stability
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Types of Radiation

• The three main types of nuclear radiation are
  alpha radiation, beta radiation, and gamma
  radiation.

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Radioactive Particles

• Alpha particle - Helium nucleus with no
  electrons 2 charge
• Beta particle - High energy stream of
  electrons -1 charge
• Gamma Rays - High energy wave which are the
  strongest No charge
• Refer to the radioactive particle sheet that can
  be found on the website for other particles.

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A look at Alpha Decay
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A look at Beta Decay
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A look at Gamma Decay
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Penetrating Powers
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Nuclear Equations

• Scientists use a nuclear equation when describing
  radioactive decay
• The mass number and atomic number must add up to
  be the same on both sides of the equation

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Balancing Nuclear Equations

• Heres the equation from the previous slide.
• The top numbers on the left side of the arrow
  the top numbers on the right side of the arrow.
• The same holds for the bottom numbers.
• USE A PERIODIC CHART for the atomic numbers if
  needed.

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Beta Decay

• Beta decay results in an increase in the atomic
  number.
• Notice how the top numbers equal and the bottom
  numbers also equal

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Nuclear Stability and Decay
For the equations on the right, the atomic
numbers are also shown but in many equations they
are omitted because they can be found on the
periodic chart. For example, carbon is often
written as 14C
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Practice

• Write the nuclear equation of the alpha decay of
  Radon 226
• Write the nuclear equation of the alpha decay of
  Gold 185
• The number after the element is the mass number.

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Practice Answers

• 226Rn ? 4He 222Po
• 185Au ? 4He 181Ir

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Practice

• Write the nuclear equation of the beta decay of
  Iodine - 131
• Write the nuclear equation of the beta decay of
  Sodium - 24

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Practice Answers

• 131I ? -1e-1 131Xe
• 24Na ? -1e-1 24Mg

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Half Life

• Radioisotopes are radioactive isotopes of
  elements (not all isotopes are radioactive)
• A half-life is the amount of time it takes for
  one half of a sample to decay.
• The half-life is different for each element and
  isotope.
• http//www.colorado.edu/physics/2000/isotopes/radi
  oactive_decay3.html

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Beta Decay of Phosphorous - 32
Notice that every 14 days, the amount is cut in
half.
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Radiocarbon Dating

• Carbon - 14 undergoes beta decay to form stable
  nitrogen 14
• Half life of 5,730 years
• Used to approximate ages 100 30,000 years
• Other radioisotopes are used to measure longer
  periods of time

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Parent and Daughter Nuclides

• The term parent nuclide refers to the original
  atom.
• The term daughter nuclide refers to the particle
  that is produced after the radioactive decay is
  completed.

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Some examples of Parent Daughter Nuclides
Parent Daughter Half Change in...
Carbon-14 Nitrogen-14 5730 years
Uranium-235 Lead-207 704 million years
Uranium-238 Lead-206 4,470 million years
Potassium-40 Argon-40 1,280 million years
Thorium-232 Lead-208 14,010 million years
Rubidium-87 Strontium-87 48,800 million years
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Practice

• The half-life of Po-218 is three minutes. How
  much of a 2.0 gram sample remains after 15
  minutes?
• Remember that the symbol for half life is t1/2

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Practice Answer

• It is often best to set up a simple table
  especially if the amount of time is a multiple of
  the half life like in this example.
• Notice that 15 minutes is a multiple of the 3
  minute half life.
• The next slide has the table that we need to
  create to solve the problem.

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Practice Answer Half Life Table
Amount of Material Initially Time elapsed Amount of material remaining
2 grams 0 minutes 2 grams
2 grams 3 minutes 1 gram
1 gram 6 minutes .5 grams
.5 gram 9 minutes .25 grams
.25 grams 12 minutes .125 grams
.125 grams 15 minutes .0625 grams
So after 15 minutes, there is only .0625 grams
left.
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Practice

• Three grams of Bismuth-218 decay to 0.375 grams
  in one hour.
• What is the half-life of this isotope?

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Practice Answer Half Life Table
We can also create the table going backwards to
answer questions like this one. Notice it is
really a similar table.
Amount of Material Initially Number of half-lives Amount of material remaining
3 grams 1 1.5 grams
1.5 grams 2 .75 grams
.75 grams 3 .375 grams
It took 3 half-lives to get to the amount .375
grams. If 1 hour equals 3 half-lives, then each
half-life must be 20 minutes.
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More on Half - Life

• Sometimes the amount of time is not a multiple of
  number of half-lives.
• We can use the following equation for all
  half-life problems.

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Nuclear Bombardment

• Nuclear scientists change elements by bombarding
  the nucleus with particles transmutation
• 14N 4He ? 17O 1H
• Leads to the creation of transuranium (after U)
  elements.

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Transmutation Reactions

• The first artificial transmutation reaction
  involved bombarding nitrogen gas with alpha
  particles.

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Fermilab Particle Accelerator







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Nuclear Power

• Nuclear Reactors use fission of Uranium-235 as
  source of energy
• A large nucleus is split into two smaller nuclei
• A small amount of mass is converted to a
  tremendous amount of energy (E mc)2
• About 1 kg of Uranium-235 2.2 million gallons
  of gasoline
• http//people.howstuffworks.com/nuclear-power2.htm
  

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Nuclear Fission

• Nuclear Fission

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Fission Produces a Chain Reaction
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Overview of a nuclear power plant
All power plants work on the same principal. It
needs to heat up water to make steam to run a
steam engine which produces the actual
electricity. The only difference between a coal
power plant and a nuclear power plant is that the
first burns coal to heat the water and the second
controls a nuclear reaction to heat the water.
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Nuclear Power Plants 1

• A nuclear plant has some differences of
  course compared to a coal burning plant.
• The fuel is much more costly, though lasts
  much longer.
• The heat can be controlled easily in a coal
  burning plant by simply controlling how much
  coal is added to the fire.
• This is the primary difference and the biggest
  safety concern in a nuclear power plant as the
  next slide shows.

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Nuclear Power Plants 2

• Uranium fuel cant be removed or limited like a
  coal fired power plant.
• The heat comes from the chemical reaction of the
  decay of a uranium atom.
• The atom splits and the chain reaction keeps it
  going.
• The way to control the heat released is by
  controlling the neutrons released
• during the chain reaction.
• This is done by using graphite rods that can be
  raised and lowered which controls the amount of
  neutrons absorbed at any time.

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Nuclear Power Plants 3

• This was the primary problem in developing the
• atomic bomb during World War 2.
• Both sides knew how to get the fission process of
  the uranium going, but the questions were on how
  to keep it under control so it wouldnt go off
  too early in the lab.
• There were two teams. One team was working for
  Germany. The other team was a group of mostly
  German scientists who were able to flee Germany
  to the United States and were working for the
  Allied forces.

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Nuclear Power Plants 4
The team working in Germany focused on using
heavy water to moderate the chain reaction.
Heavy water is regular water but with a
difference in the hydrogen isotope. Regular
water is mostly 1H but heavy water is 2H. This
extra neutron helps to absorb other neutrons and
control the reaction. Regular water is about
.0001 heavy water but the percentage needed is
about 98 so it took time to get enough heavy
water needed.
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Nuclear Power Plants 5
The allied side, based in the United States
decided to use graphite rods which could be
raised and lowered and absorb the
neutrons. While both were acceptable ways to
moderate the reaction, the Allied side was able
to create the bomb first and force an end to the
war.
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A Schematic Diagram of a Reactor Core
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Gun-triggered fission bomb (Little Boy -
Hiroshima)Implosion-triggered fission bomb (Fat
Man - Nagasaki)
http//people.howstuffworks.com/nuclear-bomb5.htm
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Nuclear Power Plants 6
An interesting side note to all of this is how
nuclear energy in power plants came to be. The
scientists who were working on the bomb were
uneasy with this type of power and the US
government put out a survey to ask how can this
energy source by used peacefully. Some answers
such as to create a new Panama Canal were tossed
aside (too much residual radiation). Suggestions
were that if the reaction can be controlled it
can be used to run steam turbines in power
plants. This led to the start of the nuclear
power plant.
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A schematic of a nuclear power plant







What the heat from the radioactive process does
is to heat water to run a turbine.
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Nuclear Fusion

• Atomic nuclei fuse releasing a tremendous
  amount of energy

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Nuclear Weapons

• The bombs dropped in World War 2 were fission
  bombs made of Uranium and getting their energy
  when the Uranium atoms split (fission) into
  smaller atoms.
• This is called an Atomic Bomb.
• Since then, the process of taking Hydrogen atoms
  and combining 4 of them to create a Helium atom
  (fusion) has been developed. This creates a more
  powerful bomb.
• This is called a Nuclear Bomb.

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Radiation and You

• SI units are in Curies (Ci)
• One Curies is amount of nuclear disintegrations
  per second from one gram of radium
• Also measured in rem (Roentgen Equivalent for
  Man)
• Over 1000 rem is fatal
• The next slide gives a glimpse of the radiation
  we receive. NOTE that the units are MILLIREMS,
  which is 1/ 1,000 of a REM.

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Radon Gas
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Figure 18.2 A Decay Series
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Detecting Nuclear Radiation

• You cannot hear or feel nuclear radiation.
• Geiger Counter
• Film badges