Nuclear Chemistry, Chapter 18
Introduction
• Remember that ISOTOPES are atoms with different masses due to different numbers of NEUTRONS.
21H 3
1H11H
• Rutherford’s Gold Foil expt. showed that all of the mass of the atom is in the nucleus. http://www.youtube.com/watch?v=NlDPPANJZXM or use the pHet Rutherford Scattering simulation: http://phet.colorado.edu/en/simulation/rutherford-scattering
• Nucleus = protons + neutrons• Together they are called NUCLEONS.• NUCLIDES are atoms identified by both mass and
number. ex: 1
• 1
H
What force holds nuclei together?
• Called the Strong Force.• Identified by Hideki Yukawa• MUCH stronger than charge interactions but
only strong over a VERY SHORT DISTANCE.• Strong force must be stronger than the force
pulling the nucleons apart (repulsion due to charge), so in large nuclei, where due to distance the pull is less, the nuclei tend to fall apart.
Are there smaller nuclear particles than neutrons and protons?
• Dalton—atoms are the smallest particles in nature
• Other scientists—there are protons and neutrons.
• 1960—protons and neutrons are made of QUARKS.
Quark FLAVORS
1. Up2. Down3. Top4. Bottom5. Strange6. Charm
ONLY Up and Down make up Protons and Neutrons.
Up
UpUpDown
Down
Down
PROTON Neutron
3 quarks make up each
The stability of a nucleusDepends on the Neuton/Proton ratio
(N/Z)
Remember: # of protons= atomic number.
Radioactive decay:The spontaneous breakdown of
unstable nuclei releasingparticles or energy.
Atomic particles:• Alpha particles: nuclei
of Helium 4 (2 pr/2neut)
•Beta Particles: electrons or positrons. •Gamma Particles: photons (actually energy—light)•Neutrons
Atomic particles: •Alpha particles: do not penetrate deeply (one sheet of paper or skin)•Beta Particles: penetrate tissues. Stopped by distance (a few sheets of aluminum foil). Lead converts it to gamma radiation.•Gamma Particles: very dangerous (x rays), stopped by several cm of lead.•Neutrons: stopped by a few cm of lead.
1N 1p + 1eBeta decay
A neutron released from an unstable nucleus can be converted intoA Proton and an Electron + energy. The Electron is also called a Beta Particle.
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch23/modes.php#radiation
http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/radioactivedecay.htm
Relevance to today:What do we use radiation for?1) Nuclear medicine (x rays penetrate tissues)2) Treating cancer (x rays can kill tumor cells—andother cells!)3) Carbon Dating of fossils4) Scientific investigations—radiolabelled compoundsAre easier to identify than unlabeled compounds.5) Nuclear power…
• Genetic damages: from mutations that alter genes
• Genetic defects can become apparent in the next generation
• Somatic damages: to tissue, such as burns, miscarriages & cancers
Bad Health Effects of Radiation
www.bio.miami.edu/beck/esc101/Chapter14&15.ppt
Electricity Production by Fuel
Electricity Production by Fuel
56%
9%
3%
23%
9%Coal
HydroelectricPowerOther
Nuclear
Natural Gass
U.S. Department of Energy, Annual Energy Review 1999
Use of Fission Power• 1945 • first large scale use• atomic bombs were used by
the US to knock Japan out of WWII– since then attention has
been given to the peaceful uses of atomic energy
Nuclear Power Plants
• In a conventional nuclear power plant–a controlled nuclear fission chain reaction
–heats water–produce high-pressure steam –that turns turbines –generates electricity.
www.bio.miami.edu/beck/esc101/Chapter14&15.ppt
Nuclear Fission• approximately 20,000 times as
much heat and energy is released from uranium fuels as from an equivalent amount of coal
• when a sufficient amount of fissionable material is brought together, a chain reaction occurs splitting atoms and releasing a tremendous amount of heat
Nuclear FissionControlled Fission Chain Reaction
neutrons split the nuclei of atoms such as Uranium or Plutonium
release energy (heat)
www.bio.miami.edu/beck/esc101/Chapter14&15.ppt
http://www.youtube.com/watch?v=vjqIJW_Qr3c
http://phet.colorado.edu/en/simulation/nuclear-fission
Nuclear Fusion• Fusion is combining together• the atoms are fused together
rather than split apart• possibilities for nuclear fusion are
much greater than those for nuclear fission
Fuel for fusion• fusion reactors would be fueled
by deuterium, an isotope of hydrogen
• available in almost unlimited supply in sea water
FusionProblems:• process is so difficult to control that it is
questionable whether commercial adaptation will ever be economically feasible
• Can be done in a lab –held in check by magnetic fields.
• BUT—creates HUGE amounts of heat.
www.bio.miami.edu/beck/esc101/Chapter14&15.ppt
Fusion Problems• fusion requires extreme pressure
and temperatures (as high as 100 million degrees)
• such heat was achieved by the Hydrogen bomb by first setting off a fission explosion
Destructive power:
[1] Small towns have been leveled by floods and landslides.
[2] The same size town could be leveled by 1,000 tons of chemical explosives.
[3] Hiroshima (quarter of a million people) was destroyed by releasing the energy in 40 kg of Uranium
We know the least about the strong nuclear force.
Nuclear Energy Concerns
• Concerns about the safety, cost, and liability have slowed the growth of the nuclear power industry
• Accidents at Chernobyl and Three Mile Island, and more recently, Fukashima, showed that a partial or complete meltdown is possible
Chernobyl•April 26, 1986, reactor explosion (Ukraine) flung radioactive debris into atmosphere
•Health ministry reported 3,576 deaths•Green Peace estimates 32,000 deaths;•About 400,000 people were forced to leave their homes
•~160,000 sq km (62,00 sq mi) contaminated•> Half million people exposed to dangerous levels of radioactivity
•Cost of incident > $358 billion
www.bio.miami.edu/beck/esc101/Chapter14&15.ppt
Three Mile Island•March 29, 1979, a reactor near Harrisburg, PA lost coolant water because of mechanical and human errors and suffered a partial meltdown
•50,000 people evacuated & another 50,000 fled area
•Unknown amounts of radioactive materials released
•Partial cleanup & damages cost $1.2 billion
•Released radiation increased cancer rates.
www.bio.miami.edu/beck/esc101/Chapter14&15.ppt
Three Mile Island• evacuation of preschool children
and pregnant women within five miles of the plant
1. Low-level radiation (Gives of low amount of radiation)• Sources: nuclear power plants, hospitals &
universities• 1940 – 1970 most was dumped into the ocean• Today deposited into landfills
2. High-level radiation (Gives of large amount of radiation)• Fuel rods from nuclear power plants• Half-time of Plutonium 239 is 24000 years• No agreement about a safe method of storage
Radioactive Waste
www.bio.miami.edu/beck/esc101/Chapter14&15.ppt
Radioactive Waste1. Bury it deep underground.
• Problems: i.e. earthquake, groundwater…2. Shoot it into space or into the sun.
• Problems: costs, accident would affect large area.3. Bury it under the Antarctic ice sheet.
• Problems: long-term stability of ice is not known, global warming
4. Most likely plan for the US• Bury it into Yucca Mountain in desert of Nevada • Cost of over $ 50 billion• 160 miles from Las Vegas• Transportation across the country via train & truck
www.bio.miami.edu/beck/esc101/Chapter14&15.ppt
What is Going to Happen to Spent Fuel?
Photos from :The Yucca Mountain Project:
http://www.ymp.gov/
Abandoned Idea!NIMBY!!
http://hereandnow.wbur.org/2014/02/28/nuclear-radiation-carlsbad
Conclusion……• “The odds of an American dying
from a nuclear power accident are 300 million to one.”